Display device and process for production thereof

ABSTRACT

A display device includes a first substrate and a second substrate disposed opposite to each other, and a display medium including an insulating liquid and electrophoretic colored particles dispersed therein and disposed between the first and second substrates. A first electrode and a second electrode are provided for applying a voltage to the display medium so as to move the colored particles between the first and second electrodes to effect a display depending on a voltage applied to the first and second electrodes. The electrophoretic colored particles are distributed uniformly without localization by incorporating the display medium in a plurality of light-transmissive tubes, and disposing and fixing the plurality of tubes in intimate contact with each other between the first and second substrates.

This is a divisional application of U.S. Pat. application Ser. No.09/572,328, filed on May 18, 2000 now U.S. Pat. No. 6,876,476.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a display device of the type whereinelectrophoretic particles or charged migrating particles are moved toeffect a display, and a process for producing such a display device.

In recent years, accompanying the progress of data processing apparatus,there has been an increasing demand for a display device requiring asmall power consumption and a small thickness, and extensive study anddevelopment have been made on devices satisfying such a demand. Amongthese, a liquid crystal display device wherein an alignment of liquidcrystal molecules is electrically controlled to change opticalcharacteristics has been extensively developed and commercialized as adisplay device satisfying the demand described above.

However, such liquid crystal display devices are still accompanied withproblems of visual load on human eyes, such as difficulty of recognizingcharacters on display depending on a viewing angle or due to reflectionlight, and flickering and low luminance of light sources. Accordingly,extensive study is still made for new-types of display devices causingless visual load on human eyes.

Reflection-type display devices are expected from the viewpoints oflower power consumption and less visual load on human eyes. As a typethereof, there has been known an electrophoretic display device. Asillustrated in FIGS. 13A and 13B, such an electrophoretic displaydevice, in principle, includes a pair of electrodes 33 and 34 disposedopposite to each other and a dispersion layer DL comprising a mixture ofcharged electrophoretic particles 31 and an insulating liquid 32. In thedisplay, when a voltage is applied across the dispersion layer DLbetween the electrodes 33 and 34, the charged electrophoretic particles31 are attracted toward an electrode of a polarity opposite to thecharge polarity thereof.

Incidentally, in such an electrophoretic display device, theelectrophoretic particles 31 may be colored, and also the insulatingliquid 32 may be colored, e.g., by dyeing, so as to effect a colordisplay. More specifically, when the colored electrophoretic particles31 are attached to the electrode 33 surface disposed closer to a vieweras shown in FIG. 13B, the colors of the electrophoretic particles 31 isdisplayed, and on the other hand, when the electrophoretic particles 31are attached to the electrode 34 surface disposed remoter from theviewer as shown in FIG. 13A, the color of the dyed insulating liquid 32is displayed.

Another type of electrophoretic display device as illustrated in FIGS.14A and 14B has been proposed by, e.g., Japanese Laid-Open PatentApplication (JP-A) 49-24696, wherein a pair of neighboring electrodesare disposed on one substrate so as to effect a display by movingelectrophoretic particles parallel to the substrates. Referring to FIGS.14A and 14B, the electrophoretic display device includes a transparentelectrode 35 and an opaque electrode 36 juxtaposed on one substrate 37.

Now, if the electrophoretic particles 31 are colored in black and thesubstrate 37 is colored in white, when the electrophoretic particles 31are attached to the opaque electrode 36 surface as shown in FIG. 14A,external light 38 is transmitted through a transparent electrode 35 andreflected by the white substrate 37, whereby the portion of thetransparent electrode 35 substantially looks white. On the other hand,when the electrophoretic particles 31 are attached to the transparentelectrode 35 surface as shown in FIG. 14B, the device (or cell) looksblack because of little reflection light.

When such an electrophoretic display device is repetitively used for along period, the density distribution of the electrophoretic particles31 is liable to be biased or ununiform, thus causing displayirregularity. In order to obviate such biased density distribution, ithas been proposed to divide the dispersion layer into small sections(cells) by disposing partitioning in walls at a certain interval, e.g.,by JP-A 59-34518 and JP-A 2-284124.

Further, JP-A 1-114828 has proposed a method of disposing porous spacersswellable with a dispersion medium, followed by injection of adispersion system to cause the swelling of the spacers to definediscrete small sections. In this method, a plurality of partitioningwalls defining discrete small sections are formed substantiallysimultaneously with injection of the dispersion system, so that separateformation of the partitioning wall is unnecessary.

Incidentally, a type of display device including a plurality oflight-transmissive tubes has been proposed by JP-A 49-96694, wherein aplurality of tubes filled with a liquid crystal material are disposedparallel to each other to provide a display device having a uniformthickness and capable of preventing intrusion of moisture and gas fromthe environment.

However, in such a known electrophoretic display device wherein thedispersion layer is divided into small sections (cells) by formingpartitioning walls at certain intervals for obviating ununiform densitydistribution of electrophoretic particles, the electrophoretic particleshave to be evenly distributed to respective cells, but such distributionis not easy. Further, a series of production steps including formationof partitioning walls on a substrate, uniform distribution of a displaymedium comprising a mixture of electrophoretic particles and aninsulating liquid and sealing of the display medium, requires much timeand a substantial cost.

Further, in the case of color display using plural colors ofelectrophoretic particles and/or insulating liquid sealed within cellsseparated by partitioning walls, the mixing of colors between adjacentcells is liable to be caused during the production process, so thatselective filling of electrophoretic particles or insulating liquid of adesired color is difficult and therefore a further difficulty isencountered.

SUMMARY OF THE INVENTION

In view of the state of prior art as described above, a principal objectof the present invention is to provide an (electrophoretic) displaydevice capable of reducing display irregularity and yet capable ofproduction at a reduced cost.

According to the present invention, there is provided a display device,comprising: a first substrate and a second substrate disposed oppositeto each other, a display medium comprising an insulating liquid andelectrophoretic colored particles dispersed therein and disposed betweenthe first and second substrates, and a first electrode and a secondelectrode for applying a voltage to the display medium so as to move thecolored particles between the first and second electrodes to effect adisplay depending on a voltage applied to the first and secondelectrodes; wherein

-   -   a plurality of light-transmissive tubes are each filled with the        display medium and are disposed in intimate contact with each        other between the first and second substrates.

In the display device, both the first electrodes and the secondelectrodes are disposed on the first substrate, so that the coloredparticles are moved parallel to the substrates by the voltage appliedbetween the first and second electrodes; or

-   -   the first electrodes and the second electrodes are disposed on        the first substrate and the second substrate, respectively, so        that the colored particles are moved in a direction vertical to        the substrates by the voltage applied between the first and        second electrodes.

Each tube may be provided with inner wall projections disposed at aregular interval in a longitudinal direction so as to obstruct themovement of the colored particles.

According to another aspect of the present invention, there is provideda display device, comprising: a first substrate and a second substratedisposed opposite to each other, a display medium comprising aninsulating liquid and electrophoretic colored particles dispersedtherein and disposed between the first and second substrates, and firstelectrodes and second electrodes for applying a voltage to the displaymedium so as to move the colored particles between a pair of firstelectrode and second electrode to effect a display depending on avoltage between the pair of first electrode and second electrode,wherein

a plurality of light-transmissive tubes are each filled with the displaymedium and are disposed parallel to each other between the first andsecond substrates,

a plurality of the first electrodes in the form of stripes are disposedbetween the first substrate and the tubes so that each first electrodeextends in alignment with an associated one tube, and

the second electrodes are disposed to intersect the first electrodes.

According to still another aspect of the present invention, there isprovided a process for producing a display device as described above,comprising:

forming a stripe first electrode on an outer surface of and in alongitudinal direction of a light-transmissive tube comprising aninsulating material,

filling the tube with a display medium comprising an insulating liquidand electrophoretic colored particles dispersed therein, and

disposing and fixing a plurality of the tube between a first substrateand a second substrate, one of which has been provided with secondelectrodes, so that the first electrode on the tube contacts the firstsubstrate. The process may include an optional step of formingprojections at a regular interval in a longitudinal direction of eachtube on an inner wall of the tube.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings, whereinidentical numerals are used to denote identical or like members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 13 (13A and 13B) and 14 (14A and 14B) are sectional viewsillustrating a structure and an operation principle of two types ofprior art electrophoretic display devices.

The other figures relate to various embodiments of the invention asfollows:

FIGS. 1 to 12, First embodiment,

FIGS. 15 to 20, Second embodiment,

FIGS. 21 to 31, Third embodiment,

FIGS. 32 to 38, Fourth embodiment,

FIGS. 39 to 43, Fifth embodiment,

FIGS. 44 to 54, Sixth embodiment,

FIGS. 55 to 64, Seventh embodiment, and

FIGS. 65 to 70, Eighth embodiment.

More specifically, FIGS. 1, 15, 21, 32, 39, 44, 55 and 61 are schematicperspective views each illustrating an organization of anelectrophoretic display device according to an embodiment of theinvention.

FIGS. 2A and 2B, 3A and 3B, 4, 5, 6, 7A and 7B; 16A and 16B, 17, 18; 22Aand 22B, 23A and 23B, 24A and 24B, 25, 26, 27A and 27B; 33A and 33B, 34Aand 34B, 35, 36; 40A and 40B; 45A and 45B, 46, 47, 48, 49A and 49B; 56Aand 56B; 62A and 62B, 63A and 63B, 64, 65A and 65B, and 66A and 66B, aresectional views for illustrating an operation of a display deviceaccording to an embodiment of the invention. Among the above, FIGS. 3Aand 3B, 23A and 23B, 34A and 34B, and 63A and 63B show longitudinalsections of tubes used in the display devices, and the other figuresshow cross sections of the tubes.

FIGS. 8A, 8B, 58A and 58B are schematic sectional views for illustratinga manner of filling a tube with a display medium.

FIGS. 9A to 9E, 10A to 10E, 11A to 11E, 12A to 12F; 19A to 19E, 20A to20E; 28A to 28F, 29A to 29E, 30A to 30E, 31A to 31F; 37A to 37F, 38A to38E; 42A to 42D, 43A to 43C; 51A to 51D, 52A to 52D, 53A to 53D, 54A to54D; 59A to 59E, 60A to 60D; 68A to 68E, 69A to 69D, and 70A to 70D, aresets of schematic sectional views, each set illustrating steps involvedin a process for producing a display device according to an embodimentof the invention.

FIGS. 41A, 41C, 50A, 57A, 57C, 67A and 67C are schematic perspectiveviews for illustrating a tube provided with an electrode on an outersurface.

FIGS. 41B, 41D, 50B, 50C, 50D, 57B, 57D, 67B and 67D are schematiccross-sectional views of such tubes provided with an electrode on anouter surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1 is a perspective view of an electrophoretic display deviceaccording to an embodiment of the present invention, and FIGS. 2A and 2Bare partial sectional views thereof for illustrating an operationprinciple thereof.

Referring to these figures, the display device includes a display mediumcomprising a transparent insulating liquid 1 and colored electrophoreticparticles 2, and light-transmissive tubes 3 each containing the displaymedium and sandwiched between a first substrate 4 and a second substrate6. Further, an insulating layer 5 is disposed on the first substrate 4,and the tubes 3 are held between the insulating layer 5 and the secondsubstrate 6. Below the insulating layer 5, second electrodes 7 arelocally formed, and first electrodes 8 (only one being shown) are formedfurther therebelow on the first substrate 4. For convenience ofillustration of an inner state, FIG. 1 shows a state of the displaydevice of which the peripheral sealing structure has been removed.

In the display device, the colored electrophoretic particles 2 chargedwithin the transparent insulating liquid 1 are moved horizontally (i.e.,in a direction parallel to the extension of the substrate surfaces)between (the positions above) the first electrode 8 and the secondelectrode 7 within each cell defined by each tube, to effect a display.For example, if the colored particles 2 in the transparent insulatingliquid 1 are collected above the first electrodes 8 by application of avoltage to the first electrodes 8 as shown in FIG. 2A, the coloredelectrophoretic particles 2 and the second electrodes 7 are observed by(or displayed to) a viewer (not shown) facing the second substrate 6.

On the other hand, when the colored particles 2 are collected atpositions above the first electrodes 8 by reversing the polarities ofthe voltage applied to the electrodes as shown in FIG. 8B, the coloredparticles 2 and the color of the insulating layer 5 (or the firstelectrode 8 or the first substrate 4) are displayed to the viewer.

According to the above-described device structure, a white-and-blackdisplay may be performed, e.g., by coloring both the second electrodes 7and the electrophoretic particles 2 in black and coloring the firstelectrode 8 in white. Further, it is also possible to effect a colordisplay by appropriately disposing a plurality of tubes containingdifferent colors of electrophoretic particles 2 and transparentinsulating liquid 1 and/or disposing a color layer colored in differentcolors as will be described hereinafter.

According to one method of arrangement of the tubes 3, the tubes 3 maybe disposed to extend parallel to the second electrodes 7 as shown inFIGS. 2A and 2B, and the colored particles 2 are moved transversely in adirection perpendicular to the longitudinal direction of the tubes 3. Onthe other hand, the tubes 3 may be disposed to extend parallel to theextension direction of stripe-form first electrodes 8 (only one beingshown) extending in a direction perpendicular to the second electrodes 7as shown in FIGS. 3A and 3B. In this arrangement, the colored particles2 are moved in a longitudinal direction of each tube 3.

Basically, each tube 3 may have an arbitrary sectional shape as far asit does not obstruct the movement of the colored particles 2, inclusiveof a circle, an oval and a rectangle with somewhat round corners.However, in order to realize a display which is accompanied with littleirregularity and easy-to-see for a viewer, a shape providing a largedisplay region and allowing a uniform movement of the colored particles2 is desired. For this purpose, it is preferred for a tube 3 to have aninner diameter X1 in a direction parallel to the substrates 4 and 6 andY1 in a direction perpendicular to the substrates 4 an 6 (as shown inFIG. 2B) satisfying Y1≦X1.

As briefly mentioned above, in such a display device, a color displaymay be effected by using plural colors of transparent insulating liquid1, plural colors of electrophoretic particles 2 and/or a color layer ofone or more colors disposed on the first substrate 4.

Some examples of such a display device capable of color display will nowbe described.

FIG. 4 is a schematic sectional view of a display deice for performing acolor display by using plural colors of transparent insulating liquid.Referring to FIG. 4, the display device includes three types (Y, M andC) of tubes 3 containing white electrophoretic particles 2, andtransparent insulating liquids 10, 11 and 12 of yellow (Y), magenta (M)and cyan (C), respectively, arranged in a regular manner. Further, thedisplay device is designed to be observed through a first substrate 4 byforming light-transmissive first electrodes 8 thereon.

By using the display device, yellow display may be performed bycollecting the white particles 2 on the second electrode 7 in a tube 3containing a yellow (Y)-colored insulating liquid 10, and collecting thewhite particles 2 on the first electrode 8 in the other tubes 3containing a magenta (M)-colored insulating liquid 11 and a cyan(C)-colored insulating liquid 12.

Further, if the white particles 2 in all the tubes 3 containing the Y-,M- and C-colored insulating liquids 10, 11 and 12 are collected on thefirst electrode 8 in the respective tubes as shown in FIG. 4, whitedisplay may be performed. On the other hand, if the white particles inall the tubes 3 are collected on the second electrodes 7 in therespective tubes, a black display may be performed.

FIG. 5 is a schematic sectional view of a display device for performinga color display by using plural colors of electrophoretic particles.Referring to FIG. 5, the display device includes three type of tubescontaining a transparent insulating liquid 1, and electrophoreticparticles 13, 14 and 15 of yellow (Y), magenta (M) and cyan (C),respectively arranged in a regular manner. Further, the display deviceis designed to be observed through a second substrate 6 by usingwhite-colored first electrodes 8 or inserting a white colored layer (notshown) between the first electrodes 8 and second electrodes 7. It isdesirable in this case that the second substrate 6 is provided withmasking portions 16 colored in, e.g., white or black corresponding tothe second electrodes 7 on the first substrate 4.

By using the display device, yellow display may be performed bycollecting the yellow (Y) particles 13 on the first electrodes 8 andcollecting the magenta (M) and cyan (C) particles 14 and 15 on thesecond electrodes 7. Further, if all the colored particles 13, 14 and 15are collected on the first electrodes 8 as shown in FIG. 5, a blackdisplay is performed, and on the other hand, if all the coloredparticles 13, 14 and 15 are collected on the second electrodes 7, awhite display is performed.

FIG. 6 is a schematic sectional view of a display device for performinga color display by forming colored layers on a first substrate 4.Referring to FIG. 6, the display device includes colored layers 17, 18and 19 of yellow (Y), magenta (M) and cyan (C), respectively, juxtaposedwith associated second electrodes 7 in respective tubes 3.

It is also possible to dispose the colored layers 17(Y), 18(M) and 19(C)between the first substrate 4 and the insulating layer 5, or on the backof the first substrate 4 so far as they can be observed from a viewer.The colored layers can be formed locally or over the entire region atthe respective places. It is also possible to dispose a colored ornon-colored light-reflection layer (not shown) below the colored layers17, 18 and 19.

In this embodiment, electrophoretic particles 15 are colored in white,and by moving the white electrophoretic particles 15 similarly as in thedevice of FIG. 4, respective colors may be displayed as desired.

In the color display devices of FIGS. 4, 5 and 6, the colors of thecolored particles 2, 13, 14 and 15, the first electrodes 8 and thecolored layers 17, 18 and 19 may be the colors of the materialsconstituting them, the colors of pigments contained therein, or thecolors of the coatings thereon. Each of the colored particles 2, 13, 14and 15 may comprise a single material, or two or more materials. In theabove embodiment, three colors of yellow (Y), magenta (M) and cyan (C)are used, but other arbitrary colors may be used depending on displayenvironment or display pictures. It is also possible to effect a colordisplay by using ultraviolet light or infrared light.

In the display device of this embodiment, the colored particles aremoved horizontally, i.e., in a direction parallel to the display surfaceso that a gradation display of an objective color may be effected. Forexample, this may be effected, e.g. by moving colored particles 2 frompositions above the second electrodes 7 as shown in FIG. 7A partially topositions above the first electrodes 8 as shown in FIG. 7B.

Such a partial movement of colored particles 2 may be effected, e.g., byusing a shorter voltage application time or a smaller applied voltage,using a mixture of particles having different chargeabilities, or usinga mixture of particles of different sizes.

Next, a process for producing such a display device will be described.

First, a light-transmissive tube 3 is filled with a display mediumcomprising a transparent insulating liquid 1 and colored electrophoreticparticles 2. In this embodiment, the tube 3 may have a circular orelliptical section, and may comprise a polymer, such as acrylic resin,polystyrene, polyethylene terephthalate (PET), polyether-sulfone (PES)or gelatin, or an inorganic material, such as glass or quartz,respectively exhibiting a high transmittance for visible light. It isparticularly preferred to use a polymer rich in flexibility. Thediameter of the tube may be determined appropriately depending on thesize of a display pixel. The tube 3 may preferably have a wall thicknessof, e.g., 5-30 μm, while it can vary depending on the material thereof.

The transparent insulating liquid may comprise a colorless transparentliquid, selected from, e.g., oils, such as silicone oil and olive oil;aromatic hydrocarbons, such as toluene and xylene; aliphatichydrocarbons inclusive of paraffinic hydrocarbons, such as normalparaffins and isoparaffins; halogenated hydrocarbons and high puritypetroleum fractions, which preferably have a low viscosity and provide astable charge to the electrophoretic particles 2 therein. Among these,silicone oil and isoparaffin may preferably be used. Commercial examplesof isoparaffin may include: “Shel-Sol 70, 71 and 72” available fromShell Japan K.K., “Isopar G, H, L and M” available from Exxon ChemicalK.K., and “IS Solvent 1620, 2028 and 2835” available from IdemitsuSekiyu Kagaku K.K. For the purpose of adjustment of specific gravitywith the electrophoretic particles 2, a species of insulating liquidhaving a larger specific gravity may be admixed as desired. Forproviding a colored insulating liquid 1 for color display, the colorlesstransparent insulating liquid is colored by dissolving or dispersing adye or a pigment therein.

The colored electrophoretic particles 2 may comprise a materialchargeable in the transparent insulating liquid, examples of which mayinclude titanium oxide (white), aluminum oxide (white), a mixture of aresin such as polyethylene, polystyrene or acrylic resin with acolorant.

Examples of the colorant may include known wide variety of dyes andpigments, inclusive of: carbon black, Phthalocyanine Blue, IndanthereneBlue, Peacock Blue, Permanent Red, Lake Red, Rhodamine Lake, HansaYellow, Permanent Yellow, and Benzidine Yellow. The coloredelectrophoretic particles 2 may ordinarily have a particle size(diameter) in a range of 0.1 μm to 50 μm, preferably 0.1-10 μm.

The electrophoretic particles 2 may preferably constitute 0.2-10 wt. %,more preferably 1-5 wt. % of the display medium.

The tube 3 may be filled with the display medium comprising theinsulating liquid 1 and the particles 2, e.g., in a manner asillustrated in FIG. 8A wherein one end of a tube 3 is inserted into thedisplay medium comprising the insulating liquid 1 and the particles 2under sufficient stirring in an appropriate vessel 21, and the other endof the tube 3 is sucked to fill the tube 3 simultaneously with theinsulating liquid 1 and the particles 2, or in a manner as illustratedin FIG. 8B wherein the particles 2 are uniformly attached to the innerwall of a tube 3, and then the insulating liquid 1 is introduced intothe tube 3.

After filling the tube 3 with the display medium, both ends of the tube3 are sealed up, e.g., by heating.

A plurality of tubes 3 each filled with the display medium in theabove-described manner may be disposed between a pair of substratesaccording to a process as illustrated in FIGS. 9A to 9E. First of all,as illustrated in FIG. 9A, first electrodes 8 are formed in a pattern(of, e.g., parallel stripes) on a first substrate 4. The first substrate4 may comprise a material exhibiting high transmittance to visible lightand having high heat-resistance, examples of which may include: films orsheets of polymers, such as polyethylene terephthalate (PET) andpolyether-sulfone (PES), and inorganic materials, such as glass andquartz. The first electrodes 8 may comprise any electroconductivematerial capable of patterning. For providing transparent firstelectrodes 8, indium tin oxide (ITO) may for example be used.

Then, the first electrodes 8 are coated with a lower portion ofinsulating layer 5, and second electrodes 7 are formed thereon instripes extending perpendicularly to the first electrodes 8 and furthercoated with the remaining portion of insulating layer 5 to form astructure as shown in FIG. 9B. The insulating layer 5 may preferablycomprise a film free from pinholes, such as highly transparent polyimideor acrylic resin. The second electrodes 7 may comprise a materialsimilar to that of the first electrodes 8.

The first substrate 4 may be colored for a color display as describedabove, e.g., by utilizing the color of the electrode material or theinsulating layer material per se or by disposing a layer of a coloredmaterial on the electrodes, the insulating layer or the substrate. It isalso possible to mix a colorant or a colored material within theinsulating layer.

Then, on the insulating layer 5 formed on the first substrate 4, aprescribed number of tubes 3 each filled with the display mediumcomprising the colored electrophoretic particles 2 and the transparentinsulating liquid 1 are disposed as shown in FIG. 9C. In the case ofcolor display, the tubes 3 containing different colors of coloredparticles 2 or transparent insulating liquid 1 in an appropriatelyprescribed order, e.g., in the order of yellow (Y), magenta (M) and cyan(C).

Then, a second substrate 6 is placed above the tubes 3 in alignmentwitih the first substrate 4 as shown in FIG. 9D, and the first andsecond substrates 4 and 6 are bonded to each other. For the bonding,e.g., a curable acrylic resin optionally diluted with a volatile solventmay be applied in a thin layer on at least one of the first and secondsubstrates 4 and 6. As an alternative method, the structure shown inFIG. 9D installed within an outer frame (not shown) may be heated viathe outer frame to bond the first and second substrates 4 and 6 under aslight pressure. In this instance, the tubes 3 are deformed under the aslight pressure (and optionally heat) to provide a laminate structure asshown in FIG. 9E, wherein the tubes 3 are juxtaposed in intimate contactwith each other. Further, the structure is provided with a voltageapplication means for applying voltages between the first and secondelectrodes 8 and 7, thereby providing an objective display device.

According to this embodiment described above, a plurality oflight-transmissive tubes 3 filled with a display medium comprising atransparent insulating liquid 1 and colored electrophoretic particles 2are arranged and fixed in intimate contact with each other, whereby auniform dispersion of the electrophoretic particles 2 and thetransparent insulating liquid 1 between a pair of substrates required inproduction of an electrophoretic display device can be easily performed.Further, the time-consuming and troublesome step of formation ofpartitioning walls on a substrate becomes unnecessary. As a result,electrophoretic display devices can be produced at a reduced cost and anincreased yield.

Further, as the colored electrophoretic particles are moved only withina tube 3, the uneven distribution or localization of the coloredparticles can be reduced to obviate a display irregularity. Theabove-prepared display device can be used for a binary display, afull-color display and also a gradational display and can realize adisplay with a large viewing angle and a high contrast.

Some examples according to this embodiment will be describedhereinbelow.

EXAMPLE 1

A display device of 5 cm-square in plane size was produced in thefollowing manner through a process as illustrated in FIG. 8A and FIGS.9A-9E.

First of all, a cylindrical light-transmissive tube 3 of PET having alength of 5 cm, a thickness of 3-8 μm and an inner diameter of 200 μmwas filled with a display medium which was a 30:1 (by weight)-mixture ofa transparent insulating liquid 1 of silicone oil and blackelectrophoretic particles 2 of a polystyrene-carbon mixture havingparticle sizes of ca. 1-2 μm in a manner as illustrate in FIG. 8A, i.e.,by dipping one end of the tube 3 into a bath of the display medium undersufficient stirring in a vessel 21 and sucking from the other and thetube 3. After the filling, both ends of the tube 3 were sealed up byheating.

Then, on a light-transmissive first substrate 4 of 200 μm-thick PETfilm, an ITO film was formed and patterned into first electrodes 8 inthe form of 190 μm-wide stripes (only one thereof being shown in FIG.9A) arranged at a pitch of 200 μm. Then, the first electrodes 8 werecoated with a lower half of insulating layer 5 of 4 μm-thick acrylicresin layer film colored in white with inclusion of titanium oxide fineparticles.

Further, on the insulating layer 5, a dark-black colored layer oftitanium carbide was formed and patterned by photolithography includingdry etching into second electrodes 7 of 50 μm-wide stripes at a pitch of200 μm extending perpendicular to the stripes of first electrodes 8.Further, the second electrodes 7 were coated with an upper half ofinsulating layer 5 of 2 μm-thick acrylic (FIG. 9B).

Then, on the first substrate 4 having a structure as shown in FIG. 9B, aplurality of the tubes 3 filled with the display medium of theinsulating liquid 1 and the black electrophoretic particles 2 werearranged so that their extending directions were parallel to theextension direction of the second electrodes 7 (FIG. 9C). Then, alight-transmissive second substrate 6 was disposed above the tubes 3(FIG. 9D), and the substrates 4 and 6 aligned with each other werebonded to each other with an ultraviolet-curable acrylic resin under aslight pressure between the substrates 4 and 6.

As a result, the upper and lower parts of the tubes 3 were made flat bycontact with the substrates 6 and 4, and the tubes 3 were disposed inintimate contact with each other, i.e., with no gap between each other(FIG. 9E). Further, the structure was provided with a voltageapplication means to complete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for a display to be observed from the second substrate 6 side.As a result, as the black electrophoretic particles 2 were positivelycharged in the silicone oil 1, the particles 2 were moved to positionsabove the first electrodes 8 when the first electrodes 8 were suppliedwith −50 volts, thus providing a black display state.

On the other hand, when the second electrodes 7 were supplied with −50volts, the black particles 2 were collected above the dark black-coloredsecond electrodes 7 so that the display device exhibited a grayish whitedisplay state. The response speed was 30 msec or shorter. No displayirregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 2

A display device was prepared through a process as illustrated in FIGS.10A-10E.

Tubes 3 were filled with the same display medium and in the same manneras in Example 1. Further, a first substrate 4 was provided with firstelectrodes 8, an insulating layer 5 and second electrodes 7 as shown inFIGS. 10A-10B in the same manner as in Example 1.

Then, the above-prepared tubes 3 filled with the display medium werearranged in a similar manner as in Example 1 except that they werearranged with their longitudinal directions parallel to the extensiondirection of the first electrodes 8 (FIG. 10C). Thereafter, a secondsubstrate 6 was disposed thereabove (FIG. 10D) and the substrates 4 and6 were bonded to each other in the same manner as in Example 1 to form astructure shown in FIG. 10E, which was then provided with voltageapplication means to complete a display device.

The thus-prepared display device was driven by application of ±50 voltsbetween the electrodes, whereby a display with no display irregularitydue to localization of the colored particles was performed at a responsespeed of 30 msec or shorter.

EXAMPLE 3

A display device was produced in the following manner through a processas illustrated in FIG. 8B and FIGS. 9A-9E.

First of all, cylindrical light-transmissive tubes 3 of polyethyleneterephthalate (PET) each having an inner diameter of 200 μm were filledwith three colors of display media comprising three colors oftransparent insulating liquid 1 of silicone oil dyed in yellow (Y),magenta (M) and cyan (C), respectively, and white electrophoreticparticles 2 of titanium oxide fine powder having particle sizes of ca.1-2 μm in a manner as illustrate in FIG. 8B, i.e., by dipping one end ofeach tube 3 containing white electrophoretic particles 2 uniformlyattached to the inner wall thereof into a both of insulating liquid 1dyed in a prescribed color and introducing the colored insulating liquid1 by sucking from the other end of the tube 3. After the filling, bothends of each tube 3 were sealed by heating. Thus, three types of tubes 3containing three colors of insulating liquid 1 were prepared.

Separately, a first substrate 4 was provided with first electrodes 8, aninsulating layer 5 and second electrodes 7 as shown in FIGS. 9A-9B inthe same manner as in Example 1.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions parallel to the extension direction of thesecond electrodes 7 (FIG. 9C). Thereafter, a second substrate 6 wasdisposed thereabove (FIG. 9D), and the substrates 4 and 6 were bonded toeach other in the same manner as in Example 1 to form a structure shownin FIG. 9E, which was then provided with voltage application means tocomplete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the white electrophoretic particles 2 of titaniumoxide were negatively charged in the silicone oil 1, the white particles2 were moved to positions above the first electrodes 8 to provide awhite display state when the first electrodes 8 were supplied with +50volts.

On the other hand, when the second electrodes 7 were supplied with +50volts, the white particles 2 were moved to above the second electrodes7, the respective colors of the transparent insulating liquid 1 could beobserved. The response speed was 30 msec or shorter, and no displayirregularity due to localization of the colored particles was observed.Further, by collecting the colored particles 2 above the secondelectrodes 7 at selected tubes 3, the respective colors of yellow (Y),magenta (M) and cyan (C) could be selectively exhibited to allow a colordisplay.

EXAMPLE 4

A display device was produced in the following manner through a processas illustrated in FIG. 8B and FIGS. 11A-11E.

First of all, cylindrical light-transmissive tubes 3 of PET each havingan inner diameter of 200 μm were filled with three colors of displaymedia comprising a transparent insulating layer 1 of silicone oil andthree colors of electrophoretic particles 2 comprising mixtures ofpolystyrene and colorants of yellow (Y), magenta (M) and cyan (C),respectively, and having particle sizes of ca. 1-2 μm.

The three types of tubes 3 were each prepared through a filling processas illustrated in FIG. 8B.

Separately, a first substrate 4 of 200 μm-thick PET was provided withwhite-colored first electrodes 8, an insulating layer 5 and 50 μm-wideblack-colored second electrodes 7 of titanium carbonate as shown inFIGS. 11A-11B in a similar manner as in Example 1.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions parallel to the extension direction of thesecond electrodes 7 (FIG. 11C). Thereafter, a light-transmissive secondsubstrate 6 provided with masking stripe patterns 16 of darkblack-colored titanium carbonate at parts corresponding to the secondelectrodes 7 was disposed above the first substrate 4 (FIG. 11D), andthe substrates 4 and 6 were bonded to each other in the same manner asin Example 1 to form a structure shown in FIG. 11E, which was thenprovided with voltage application means to complete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the polystyrene-based electrophoretic particles 13,14 and 15 of respective colors were positively charged in the siliconeoil 1, the colored particles were moved to positions above the firstelectrodes 8 to provide respective color display states when the firstelectrodes 8 were supplied with −50 volts.

On the other hand, when the second electrodes 7 were supplied with −50volts, the colored particles 13, 14 and 15 were moved to above thesecond electrodes 7, the first electrodes 8 could be observed throughthe transparent insulating liquid 1 to provide a white display state.The response speed was 30 msec or shorter, and no display irregularitydue to localization of the colored particles was observed. Further, bycollecting the respective colored particles 2 above the first electrodes8 at selected tubes 3, the respective colors of yellow (Y), magenta (M)and cyan (C) could be selectively exhibited to allow a color display.

EXAMPLE 5

A display device was prepared in the following manner through a processas illustrated in FIGS. 12A-12F.

Tubes 3 each having an inner diameter of 100 μm were filled with adisplay medium comprising the transparent insulating liquid 1 and whiteparticles 2 of titanium oxide, otherwise in the same manner as inExample 1.

Separately, a light-transmissive first substrate 4 of 200 μm-thick PETfilm was provided with 90 μm-wide first electrodes 8 of ITO stripes at apitch of 100 μm (FIG. 12A) and an insulating layer 5 of coloredtransparent polyimide. Further, on the insulating layer 5, a dark blacktitanium carbonate film was formed and patterned into second electrodes7 of 30 μm-wide stripes at a pitch of 100 μm extending perpendicularlyto the stripes of first electrodes 8.

Then, color layers 17 (Y), 18 (M) and 19 (C, not shown) were formed injuxtaposition with the second electrodes 7, and further coated with anupper half of insulating liquid 5 (FIG. 12C). By using the thus-treatedfirst substrate 4, a display device having a structure as shown in FIG.12F was prepared through steps as shown in FIGS. 12D to 12F otherwise inthe same manner as in Example 1.

The thus-prepared display device was driven by application of ±60 volts.The colored particles 2 of titanium oxide was negatively charged in theinsulating liquid 1 of silicone oil. As a result, the white particles 2were collected above the first electrodes 8 to provide a white displaystate when the first electrodes 8 were supplied with +60 volts.

On the other hand, when the second electrodes 7 were supplied with +60volts, the white particles 2 were collected above the second electrodes,so that the colored layers 17 and 18 (and 19 not shown) could beobserved through the second substrate 6. The response speed was 30 msecor shorter, and no display irregularity due to localization of thecolored particles 2 was observed. By forming three types colored layers(17, 18, . . . ) of yellow, cyan and magenta, a color display could beperformed.

Further, when the display device was driven at a shorter voltageapplication period of 5 msec, the reflected light of respective colorscould be lowered to nearly a half. Thus, a multi-level gradationaldisplay could be performed by selecting various voltage applicationperiods, thus providing a color display device capable of gradationaldisplay.

EXAMPLE 6

A display device of 3 cm-square was prepared through similar steps as inExample 1 by using tubes 3 having a length of 3 cm, a thickness of 2-3μm and an inner diameter of 30 μm, colored particles of ca. 0.5-1.0 μm,25 μm-wide first electrodes 8 at a pitch of 30 μm, and 10 μm-wide secondelectrodes 7 at a pitch of 30 μm.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using narrower first andsecond electrodes, the response time could be reduced to 5 msec orshorter with no display irregularity due to localization of the coloredelectrophoretic particles.

As described above, according to the present invention, a plurality oflight-transmissive tubes are filled with a display medium comprising atransparent insulating liquid and colored electrophoretic particles anddisposed in intimate contact with each other between first and secondsubstrates, whereby uniform dispersion of colored electrophoreticparticles that had been difficult heretofore has been facilitated, thusproviding a reduced display irregularity. Further, the time-consumingand troublesome step of forming partitioning walls on a substrate isunnecessitated, thus realizing a substantial reduction in productioncost.

Second Embodiment

FIG. 15 is a perspective view of an electrophoretic display deviceaccording to the embodiment, and FIGS. 16A and 16B are partial sectionalviews thereof for illustrating an operation principle thereof.

This embodiment is different from First embodiment described withreference to FIGS. 1 to 12 in that light-transmissive second electrodes7 are formed on a second substrate 6 (FIGS. 15 and 16) instead of afirst substrate 4. The other features are substantially identical tothose in First embodiment.

Referring to FIGS. 15 and 16, in the display device, coloredelectrophoretic particles 2 are moved between positions above firstelectrodes 8 and above second electrodes 7 perpendicularly to substrates4 and 6. As a result, to a viewer facing the second electrodes 6, thecolor of an insulating liquid 1 is displayed when the colored particles2 are collected above the first electrodes 8 as shown in FIG. 16A, andthe color of colored particles 2 is displayed when the colored particles2 are collected on the second electrodes 7. In this arrangement, if theelectrophoretic particles 2 are colored in black, and the insulatingliquid 1 is colored in white, a white-and-black display can beperformed.

Similarly as in First embodiment, a color display is possible alsoaccording to this embodiment. Some examples of such a display devicecapable of color display will now be described.

FIG. 17 is a schematic sectional view of a display deice for performinga color display by using plural colors of transparent insulating liquid.Referring to FIG. 17, the display device includes three types (Y, M andC) of tubes 3 containing white electrophoretic particles 2, andtransparent insulating liquids 10, 11 and 12 of yellow (Y), magenta (M)and cyan (C), respectively, arranged in a regular manner. Further, thedisplay device is designed to be observed through a second substrate 6by forming light-transmissive second electrodes 7 thereon.

By using the display device, yellow display may be performed bycollecting the white particles 2 on the first electrode 8 in a tube 3containing a yellow (Y)-colored insulating liquid 10, and collecting thewhite particles 2 on the second electrode 7 in the other tubes 3containing a magenta (M)-colored insulating liquid 11 and a cyan(C)-colored insulating liquid 12. Further, if the white particles 2 inall the tubes 3 containing the Y-, M- and C-colored insulating liquids10, 11 and 12 are collected on the first electrode 8 in the respectivetubes as shown in FIG. 17, a black display may be performed. On theother hand, if the white particles 2 in all the tubes 3 are collected onthe second electrodes 7 in the respective tubes, a white display may beperformed.

FIG. 18 is a schematic sectional view of a display device for performinga color display by using plural colors of electrophoretic particles.Referring to FIG. 18, the display device incudes three types of tubescontaining a white opaque insulating liquid 1, and electrophoreticparticles 13, 14 and 15 of yellow (Y), magenta (M) and cyan (C),respectively, arranged in a regular manner. Further, the display deviceis designed to be observed through a second substrate 6.

By using the display device, yellow display may be performed bycollecting the yellow (Y) particles 13 on the second electrodes 7 andcollecting the magenta (M) and cyan (C) particles 14 and 15 on the firstelectrodes 8. Further, if all the colored particles 13, 14 and 15 arecollected on the first electrodes 8 as shown in FIG. 18, a white displayis performed, and on the other hand, if all the colored particles 13, 14and 15 are collected on the second electrodes 7, a black display isperformed.

The materials and organizations of the insulating liquid 1, coloredelectrophoretic particles 2, 13, 14 and 15, the tubes 3, the firstelectrodes 8 and the second electrodes 7 are substantially identical tothose used in First embodiment, except that the second electrodes 7 areformed in a larger width comparable to the width of each tube 3.

Except for the above point, the display device according to thisembodiment can be produced in a similar manner as in First embodiment,e.g., through a process as shown in FIGS. 19A-19E which substantiallycorresponds to the process illustrated in FIGS. 9A-9E for Firstembodiment.

Alternatively, as shown in FIGS. 20A-20E, tubes 3 having a rectangularsection may be used and disposed in intimate contact with each other onthe second electrodes 7 (FIG. 20C), before bonding of the substrates 4and 6 to form a stacked structure as shown in FIG. 20E.

Some examples according to this embodiment will be describedhereinbelow.

EXAMPLE 7

A 5 μm-square display device was produced in the following mannerthrough a process as illustrated in FIG. 8A and FIGS. 19A-19E.

First of all, a cylindrical light-transmissive tube 3 of PET having alength of 5 cm, a wall thickness of 5-8 μm and an inner diameter of 200μm was filled with a display medium comprising a 23:1 (by weight)mixture of a white opaque insulating liquid 1 of silicone oil withlipophilic oil-soluble dye dissolved therein and black electrophoreticparticles 2 of a polystyrene-carbon mixture having particle sizes of ca.1-2 μm in a manner as illustrate in FIG. 8A, i.e., by dipping one end ofthe tube 3 into a bath of the display medium under sufficient stirringin a vessel 21 and sucking from the other and the tube 3. After thefilling, both ends of the tube 3 were sealed up by heating.

Then, on a first substrate 4 of 200 μm-thick PET film, a titanium filmwas formed and patterned into 190 μm-wide stripe first electrodes 8 at apitch of 200 μm in the form of stripes (only one thereof being shown inFIG. 19A). Separately, on a light-transmissive second substrate 6 of 200μm-thick PET film, an ITO film was formed and patterned into secondelectrodes 7 in the form of 190 μm-wide stripes at a pitch of 200 μm(FIG. 19B).

Then, on the first substrate 4 having a structure as shown in FIG. 19A,a plurality of the tubes 3 filled with the display medium of theinsulating liquid 1 and the black electrophoretic particles 2 werearranged so that their extending directions were perpendicular to theextension direction of the first electrodes 8 (FIG. 19C). Then, thesecond substrate 6 having a structure as shown in FIG. 19B was disposedabove the tubes 3 (FIG. 19D) so that the extending directions of thefirst electrodes 8 and second electrodes 7 were perpendicular to eachother, and the substrates 4 and 6 aligned with each other were bonded toeach other with an ultraviolet-curable acrylic resin under a slightpressure between the substrates 4 and 6.

As a result, the upper and lower parts of the tubes 3 were made flat bycontact with the substrates 6 and 4, and the tubes 3 were disposed inintimate contact with each other, i.e., with no gap between each other(FIG. 19E). Further, the structure was provided with a voltageapplication means to complete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for a display to be observed from the second substrate 6 side.As a result, as the black electrophoretic particles 2 were positivelycharged in the silicone oil 1, the particles 2 were moved to positionsabove the first electrodes 8 when the first electrodes 8 were suppliedwith −50 volts, thus providing a white display state (FIG. 16A).

On the other hand, when the second electrodes 7 were supplied with −50volts, the black particles 2 were collected on the second electrodes 7so that the display device exhibited a black display state (FIG. 16B).The response speed was 30 msec or shorter. No display irregularity dueto localization of the colored particles 2 was observed.

EXAMPLE 8

A display device was prepared in the same manner as in Example 7 exceptfor using a blue insulating liquid 1 formed by dissolving a blueoil-soluble dye in silicone oil and colored electrophoretic particles 2comprising white TiO₂ particles having particle sizes of ca. 1-2 μm.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the white electrophoretic particles 2 of titaniumoxide were negatively charged in the silicone oil 1, the white particles2 were moved to positions above the first electrodes 8 (FIG. 16A) toprovide a blue display state when the first electrodes 8 were suppliedwith +50 volts.

On the other hand, when the second electrodes 7 were supplied with +50volts, the white particles 2 were moved to above the second electrodes 7(FIG. 16B), thereby providing a white display state. The response speedwas 30 msec or shorter, and no display irregularity due to localizationof the colored particles was observed.

EXAMPLE 9

A display device was prepared through a process as illustrated in FIGS.20A-20E.

Tubes 3 of nylon having a nearly 200 μm×200 μm-square cross section withround corners were filled with the same display medium as in Example 7comprising the white silicone oil and black-colored particles ofpolystyrene-carbon mixture, and then both ends thereof were heat-sealed.

Then, on a first substrate 4 of 200 μm-thick PET film, a titanium filmwas formed and patterned into first electrodes 8 of 150 μm-wide stripes(FIG. 20A). Similarly, 150 μm-wide ITO stripes of second electrodes 7were formed on a light-transmissive second substrate 6 (FIG. 20B).

Then, the above-prepared tubes 3 filled with the display medium weredisposed with no spacing between each other on the second electrodes 7on the second substrate 6 so that a center line of each tube 3 wasaligned with that of an associated second electrode 7 (FIG. 20C), andthe above-treated first substrate 4 was disposed above the tubes 3 sothat the first electrodes 8 and second electrodes 7 were perpendicularto each other (FIG. 20D). Then, the substrates 4 and 6 were bonded toeach other with an acrylic resin, thereby providing a structure as shownin FIG. 20E, wherein the tubes 3 were disposed in intimate contact witheach other between the substrates 4 and 6. Further, the structure wasprovided with voltage application means to complete a display device.

The thus-prepared display device was driven in the same manner as inExample 7, whereby a display free from display irregularity due tolocalization of the colored particles 2 was performed at a responsespeed of 30 msec or shorter.

EXAMPLE 10

A display device was produced in the following manner through a processas illustrated in FIG. 8B and FIGS. 19A-19E.

First of all, cylindrical light-transmissive tubes 3 of (PET) eachhaving an inner diameter of 200 μm were filled with three colors ofdisplay media comprising three colors of transparent insulating liquid 1of silicone oil dyed in yellow (Y), magenta (M) and cyan (C),respectively, and white electrophoretic particles 2 of titanium oxidefine powder having particle sizes of ca. 1-2 μm in a manner asillustrate in FIG. 8B, i.e., by dipping one end of each tube 3containing white electrophoretic particles 2 uniformly attached to theinner wall thereof into a both of insulating liquid 1 dyed in aprescribed color and introducing the colored insulating liquid 1 bysucking from the other end of the tube 3. After the filling, both endsof each tube 3 were sealed by heating. Thus, three types of tubes 3containing three colors of insulating liquid 1 were prepared.

Separately, a first substrate 4 was provided with first electrodes 8,and second electrodes 7 were formed on a second substrate 6 as shown inFIGS. 19A-19B in the same manner as in Example 7.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions perpendicular to the extension directionof the first electrodes 8 on the first substrate 4 (FIG. 19C).Thereafter, the second substrate 6 having thereon the second electrodes7 was disposed thereabove so that the first electrodes 8 and the secondelectrodes 7 were perpendicular to each other (FIG. 19D), and thesubstrates 4 and 6 were bonded to each other in the same manner as inExample 7 to form a structure shown in FIG. 19E, which was then providedwith voltage application means to complete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the white electrophoretic particles 2 of titaniumoxide were negatively charged in the silicone oil 1, the white particles2 were moved to positions above the first electrodes 8 to displayrespective colors of the three types of the insulating liquid 1 when thefirst electrodes 8 were supplied with +50 volts (FIG. 17).

On the other hand, when the second electrodes 7 were supplied with +50volts, the white particles 2 were moved to above the second electrodes7, a white display state was exhibited. The response speed was 30 msecor shorter, and no display irregularity due to localization of thecolored particles was observed. Further, by collecting the coloredparticles 2 above the first electrodes 8 at selected tubes 3, therespective colors of yellow (Y), magenta (M) and cyan (C) could beselectively exhibited to allow a color display.

EXAMPLE 11

A display device was produced in the following manner through a processas illustrated in FIG. 8B and FIGS. 19A-19E.

First of all, cylindrical light-transmissive tubes 3 of PET each havingan inner diameter of 200 μm were filled with three colors of displaymedia comprising a white insulating liquid 1 of silicone oil dyed withoil-soluble white dye and three colors of electrophoretic particles 2comprising mixtures of polystyrene and colorants of yellow (Y), magenta(M) and cyan (C), respectively, and having particle sizes of ca. 1-2 μm.

The three types of tubes 3 were each prepared through a filling processas illustrated in FIG. 8B.

Separately, first electrodes 8 were formed on a first substrate 4 (FIG.19A), and second electrodes 7 were formed on a second substrate 6 (FIG.19B), respectively, in the same manner as in Example 7.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions perpendicular to the extension directionof the first electrodes 8 (FIG. 19C). Thereafter, the second substrate 6provided with the second electrodes 7 was disposed above the firstsubstrate 4 (FIG. 19D), so that the first electrodes 8 and the secondelectrodes 7 were perpendicular to each other, and the substrates 4 and6 were bonded to each other in the same manner as in Example 7 to form astructure shown in FIG. 19E, which was then provided with voltageapplication means to complete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the polystyrene-based electrophoretic particles 13,14 and 15 of respective colors were positively charged in the siliconeoil 1, the colored particles were moved to positions above the firstelectrodes 8 to provide a white display state due to the color of thewhite insulating liquid 1 when the first electrodes 8 were supplied with−50 volts (FIG. 18).

On the other hand, when the second electrodes 7 were supplied with −50volts, the colored particles 13, 14 and 15 were moved to above thesecond electrodes 7, the respective colors of the colored particles13(Y), 14(M) and 15(C) were observed. The response speed was 30 msec orshorter, and no display irregularity due to localization of the coloredparticles was observed. Further, by collecting the respective coloredparticles 2 above the second electrodes 7 at selected tubes 3, therespective colors of yellow (Y), magenta (M) and cyan (C) could beselectively exhibited to allow a color display.

EXAMPLE 12

A display device was prepared through similar steps as in Example 7 byusing tubes 3 having an inner diameter of 30 μm, colored particles ofca. 0.5-1.0 μm and a smaller gap of 25 μm between the substrates 4 and6.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using the smaller gap, theresponse time could be reduced to 5 msec or shorter with no displayirregularity due to localization of the colored electrophoreticparticles.

According to this embodiment, in addition to the effects of Firstembodiment, a better display clarity and contrast can be attained due toutilization of vertical movement of the colored particles.

Third Embodiment

FIG. 21 is a perspective view of an electrophoretic display deviceaccording to an embodiment of the present invention, and FIGS. 22A and22B are partial sectional views thereof for illustrating an operationprinciple thereof.

This embodiment is different from First embodiment described withreference to FIGS. 1 to 12 in that each tube 3 is provided with aplurality of projections 3 a from the inner wall thereof at prescribedintervals for obstructing the movement of colored electrophoreticparticles 2 in a longitudinal direction thereof. The other features aresubstantially identical to those in First embodiment.

Similarly as in First embodiment, the tubes 3 may be arranged so thattheir longitudinal direction is parallel to the extension direction ofthe second electrodes 7 (FIGS. 21 and 22) or parallel to the extensiondirection of the first electrodes 8 (FIGS. 23A and 23B). According tothis embodiment, as shown in FIGS. 21 and 23 and best understood fromFIGS. 23A and 23B, each tube 3 is provided a plurality of projections 3a from its inner wall at a prescribed pitch in a longitudinal directionthereof. By provision of such projections 3 a along the inner wall ofeach tube 3, the movement of the charged electrophoretic particles 2respectively moving in the insulating liquid 1 is confined within arange of space (“moving space”) partitioned by adjacent two projections3 a.

By the confinement of the electrophoretic particles 2 within a movingspace, the electrophoretic particles 2 can be uniformly distributed in atube 3 during the production, and the localization of theelectrophoretic particles 2 within a tube 2 during long hours ofcontinual operation can be reduced to reduce the display irregularity.

In the examples of FIGS. 21 to 23, each projection 3 a is formed over anentire circumference of a tube inner wall, but such a projection can beformed only partially, as far as it is effective for restricting themovement of electrophoretic particles 2 in a longitudinal direction of atube 3, e.g., only at a side of inner wall close to the first substrate4 on which the electrodes 7 and 8 (as projections 3 a′ shown in FIGS.24A and 24B). Alternately, such projections 3 a can be enlarged so as toform closed moving spaces capable of restricting the movement of notonly the electrophoretic particles 2 but also the insulating liquid 1.

Such inner projections 3 a can be provided to the tubes 3 before orafter filling the tubes 3 with the display medium comprising theinsulating liquid 1 and the electrophoretic particles 2.

Such projections 3 a can be provided to a tube 3 prior to filling withthe display medium by constricting or shortening the tube 3 by heatingor photo-illumination, or deformation at a prescribed pitch of the tube3, e.g., by pressing with a pressing tool. The diameter of the tube 3and the pitch of projections may be determined corresponding to the sizeof display pixels.

Further, such projections 3 a may be provided to a tube 3 after fillingwith the display medium, e.g., pressing the tube 3 onto the firstsubstrate or electrodes thereon provided with projections, by pressingthe tube 3 with a patterned pressing tool, or by physically twisting thetube 3.

The display device according to this embodiment may be used for colordisplay similarly as in First embodiment as shown in FIGS. 24-26(corresponding to FIGS. 4-6 for First embodiment) and or gradationaldisplay as shown in FIGS. 27A and 27B (corresponding to FIGS. 7A and 7Bfor First embodiment).

The display device according to this embodiment may be produced by usingtubes 3 already provided with or not provided with the inner wallprojections 3 a as mentioned above.

First of all, the display device may be produced by using tubes 3already provided with inner wall projections 3 through a process asillustrated in FIGS. 28A to 28F in a similar manner as described withreference to FIGS. 9A to 9E with respect to First embodiment.

In the structure shown in FIG. 28E, when the first substrate 4 and thesecond substrate 6 are bonded to each other, the projections 3 a are notfully deformed to form a complete partitioning wall, thus allowing acommunication between adjacent moving spaces S. However, it is alsopossible to cause such a full deformation to form complete partitionsand provide closed moving spaces S. In any case, the localization of theelectrophoretic particles due to movement along the longitudinaldirection within each tube can be effectively obstructed.

Then, a device production process wherein tubes 3 filled with thedisplay medium comprising the insulating liquid 1 and theelectrophoretic particles 2 are provided with inner wall projections 3 aduring the device production process will now be described withreference to FIGS. 29A to 29E. The tubes 3 subjected to this deviceproduction process can have been provided with some inner wallprojections.

Referring to FIGS. 29A and 29B, a first substrate 4 is provided withfirst electrodes 8, second electrodes 7 and an insulating layer 5 in thesame manner as in First embodiment described with reference to FIGS. 10Aand 10B (i.e., similarly as FIGS. 9A and 9B), and then projections 9 forproviding inner wall projections 3 a to the tubes 3 are formed on theinsulating layer 5. The projections 9 may comprise a similar material asthe insulating layer 5 for convenience of production but need notcomprise an insulating material. It is also possible to provide a partof the first electrodes 8 and/or second electrodes 7 with a projectingstructure. The shape and position of the projection may be appropriatelydetermined depending on the specification of the inner wall projections3 a.

Then, on the first substrate 4 provided with the projections 9, thetubes 3 filled with the display medium comprising the insulating liquid1 and the electrophoretic particles 2 are arranged (FIG. 29C), a secondsubstrate 6 is disposed above the tubes 3 in alignment with the firstsubstrate 4 (FIG. 29D), and the structure shown in FIG. 29D installedwithin an outer frame (not shown) is heated via the outer frame to bondthe substrates 4 and 6 while deforming the tube 3 to provide inner wallprojections 3 a on the first substrate 4 side (FIG. 29E).

In the above example shown in FIG. 29A-29E, the projections 9 forproviding tube inner wall projections 3 a are formed only on the firstsubstrate 4, but such projections can also be formed on the secondsubstrate 6. Further, as a result of the bonding of the substrateswithin an outer frame, the upper and lower portions of a tube 3 canpartially contact each other or form a closed partition.

Instead of the above-mentioned processes, the tubes 3 filled with thedisplay medium can be provided with such inner wall projections atregular intervals, e.g., by forming a pressing tool provided with innerprojections or by physically twisting the tubes. As a result, the tubeinner wall is provided with periodical constricted sectional portions,by pressing or twisting, which may be regarded as inner wall projectionsaccording to this embodiment. In these cases, the constricted portionscan close the tube 3 thereat. In the case of press-forming for providingsuch projections, the tubes 3 may preferably comprise a material havinga softening point which is lower than the temperatures causingdenaturation of the insulating liquid 1 and the electrophoreticparticles 2.

Except for the above points, the insulating liquid 1, theelectrophoretic particles 2 and the tubes 3 may comprise identicalmaterials as in First embodiment. The tubes 3 may be filled with thedisplay medium comprising the insulating liquid 1 and theelectrophoretic particles 2 in similar manners as in First embodiment asillustrated in FIGS. 8A and 8B. Further, the display device according tothis embodiment may be driven for white-black display, color displayand/or gradational display in similar manners as in First embodimentexcept that the localization of the electrophoretic particles 2 isbetter suppressed due to better suppression of movement of theelectrophoretic particles 2 in the longitudinal direction within eachtube 3 due to provision of the inner wall projections 3 a.

Some specific examples according to this embodiment will be describedhereinafter.

EXAMPLE 13

A display device of 5 cm-square in planar size was prepared through aprocess as illustrated in FIGS. 8A and 28A-28F.

A cylindrical light-transmissive tube 3 of PET having a length of 5 cm,a wall thickness of 10-15 μm and an inner diameter of 200 μm was locallyperiodically heated by causing heat shrinkage to be provided with innerwall projections 3 a at a pitch of 180 μm providing constricted innerwall diameters of 100-150 μm. The tube 3 was then filled with a displaymedium comprising a 25:1 (by weight)-mixture of a transparent insulatingliquid 1 of silicone oil and black electrophoretic particles 2 of apolystyrene-carbon mixture having particle sizes of ca. 1-2 μm in amanner as illustrate in FIG. 8A, i.e., by dipping one end of the tube 3into a bath of the display medium under sufficient stirring in a vessel21 and sucking from the other and the tube 3. After the filling, bothends of the tube 3 were sealed up by heating.

Then, on a light-transmissive first substrate 4 of 200 μm-thick PETfilm, an aluminum film was formed and patterned into first electrodes 8in the form of 190 μm-wide stripes at a pitch of 200 μm (only onethereof being shown in FIG. 28A). Then, the first electrodes 8 werecoated with a lower half of insulating layer 5 of 4 μm-thick acrylicresin film colored in white with inclusion of titanium oxide fineparticles.

Further, on the insulating layer 5, a dark-black colored layer oftitanium carbide was formed and patterned by photolithography includingdry etching into second electrodes 7 of 50 μm-wide stripes at a pitch of200 μm extending perpendicular to the stripes of first electrodes 8.Further, the second electrodes 7 were coated with an upper half ofinsulating layer 5 of 2 μm-thick acrylic resin (FIG. 28B).

Then, on the first substrate 4 having a structure as shown in FIG. 28B,a plurality of the tubes 3 provided with the inner wall projections 3 a(not seen in FIG. 28C) and filled with the display medium of theinsulating liquid 1 and the black electrophoretic particles 2 werearranged so that their extending directions were parallel to theextension direction of the second electrodes 7 (FIG. 28C). Then, alight-transmissive second substrate 6 was disposed above the tubes 3(FIG. 28D), and the substrates 4 and 6 aligned with each other werebonded to each other with an ultraviolet-curable acrylic resin under aslight pressure between the substrates 4 and 6.

As a result, the upper and lower parts of the tubes 3 were made flat bycontact with the substrates 6 and 4, and the tubes 3 were disposed inintimate contact with each other, i.e., with no gap between each other(FIG. 28E). Along with the deformation of the tubes 3, the verticaldistance between the upper and lower portions of each inner wallprojection 3 a was narrowed to provide moving spaces S within which themovement of the electrophoretic particles 2 were substantially confinedto form a structure as shown in FIG. 28F (and also in FIG. 28E).Further, the structure was provided with a voltage application means tocomplete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for a display to be observed from the second substrate 6 side.As a result, as the black electrophoretic particles 2 were positivelycharged in the silicone oil 1, the particles 2 were moved to positionsabove the first electrodes 8 when the first electrodes 8 were suppliedwith −50 volts, thus providing a black display state.

On the other hand, when the second electrodes 7 were supplied with −50volts, the black particles 2 were collected above the dark black-coloredsecond electrodes 7 so that the display device exhibited a grayish whitedisplay state. The response speed was 30 msec or shorter. No displayirregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 14

A display device was prepared through a process as illustrated in FIGS.8B and 29A-29E.

A cylindrical light-transmissive tube 3 identical to the one used inExample 13 provided with no inner wall projections was filled with thesame display medium as in Example 13 but in a manner as illustrated inFIG. 8B, i.e., by dipping one end of the tube 3 containing blackelectrophoretic particles 2 uniformly attached to the inner wall thereofinto a bath of transparent insulating liquid 1 and introducing thecolored insulating liquid 1 by sucking from the other end of the tube 3.After the filling, both ends of the tube 3 were sealed by heating. Thus,a plurality of tubes 3 containing the display medium were prepared.

Separately, a first substrate 4 was provided with first electrodes 8(FIG. 29A), and second electrodes 7 and an insulating layer 5 in thesame manner as in Example 13, and then further provided with 30 μm-highand 15 μm-wide stripe-shaped projections 9 a of acrylic resin arrangedat a pitch of 300 μm in parallel with the second electrodes 7 (FIG.29B). Then, the above-prepared tubes 3 filled with the display mediumwere arranged on the first substrate 4 with their extension directionsperpendicular to the extension directions of the projections 9 (FIG.29C). Thereafter, a second substrate 6 was disposed thereabove (FIG.29D) and the substrates 4 and 6 were bonded to each other in the samemanner as in Example 13 to form a structure shown in FIG. 29E. Thus, thetubes 3 were disposed in intimate contact with each other and with theirupper and lower surfaces made flat and in intimate contact with thesecond substrate 6 and the first substrate 4 while the lower surface wasprovided with inner wall projections 3 a corresponding to theprojections 9 to form moving sections (FIG. 29E). The structure was thenprovided with voltage application means to complete a display device.

The thus-prepared display device was driven by application of ±50 voltsbetween the electrodes, whereby a display with no display irregularitydue to localization of the colored particles was performed at a responsespeed of 30 msec or shorter.

EXAMPLE 15

A color display device was prepared through a process as illustrated inFIGS. 28A-28E.

Cylindrical light-transmissive tubes 3 of PET were provided with innerwall projections 3 a in the same manner as in Example 13, and thenfilled with three colors of display media comprising three colors oftransparent insulating liquid 1 of silicone oil dyed in yellow (Y),magenta (M) and cyan (C), respectively, and white electrophoreticparticles 2 of titanium oxide fine powder having particle sizes of ca.1-2 μm. After the filling, both ends of each tube 3 were sealed byheating. Thus, three types of tubes 3 containing three colors ofinsulating liquid 1 were prepared.

Separately, a first substrate 4 was provided with first electrodes 8, aninsulating layer 5 and second electrodes 7 as shown in FIGS. 28A-28B inthe same manner as in Example 13.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions parallel to the extension direction of thesecond electrodes 7 (FIG. 28C). Thereafter, a second substrate 6 wasdisposed thereabove (FIG. 28D), and the substrates 4 and 6 were bondedto each other in the same manner as in Example 13 to form a structureshown in FIG. 28E. At this time, the upper and lower portion of eachprojection 3 a were made closer to each other to form a structure asshown in FIG. 28E having moving sections S. The structure was thenprovided with voltage application means to complete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the white electrophoretic particles 2 of titaniumoxide were negatively charged in the silicone oil 1, the white particles2 were moved to positions above the first electrodes 8 to provide awhite display state when the first electrodes 8 were supplied with +50volts.

On the other hand, when the second electrodes 7 were supplied with +50volts, the white particles 2 were moved to above the second electrodes7, the respective colors of the transparent insulating liquid 1 could beobserved. The response speed was 30 msec or shorter, and no displayirregularity due to localization of the colored particles was observed.Further, by collecting the colored particles 2 above the secondelectrodes 7 at selected tubes 3, the respective colors of yellow (Y),magenta (M) and cyan (C) could be selectively exhibited to allow a colordisplay.

EXAMPLE 16

A display device was produced in the following manner through a processas illustrated in FIG. 8B and FIGS. 30A-30E.

First of all, cylindrical light-transmissive tubes 3 of PET each havingan inner diameter of 200 μm were filled with three colors of displaymedia comprising a transparent insulating layer 1 of silicone oil andthree colors of electrophoretic particles 2 comprising mixtures ofpolystyrene and colorants of yellow (Y), magenta (M) and cyan (C),respectively, and having particle sizes of ca. 1-2 μm.

The three types of tubes 3 were each prepared through a filling processas illustrated in FIG. 8B. Further, the tubes 3 were each provided withinner wall projections at a pitch of 200 μm by means of a pressing tool.

Separately, a first substrate 4 of 200 μm-thick PET was provided withwhite-colored first electrodes 8, an insulating layer 5 and 50 μm-widesecond electrodes 7 of titanium carbonate as shown in FIGS. 30A-30B in asimilar manner as in Example 13.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions parallel to the extension direction of thesecond electrodes 7 (FIG. 25 and FIG. 30C). Thereafter, alight-transmissive second substrate 6 provided with masking stripepatterns 16 of dark black-colored titanium carbonate at partscorresponding to the second electrodes 7 was disposed above the firstsubstrate 4 (FIG. 30D), and the substrates 4 and 6 were bonded to eachother in the same manner as in Example 13 to form a structure shown inFIG. 30E, further provided with inner wall projections 3 a (not shown).The structure was then provided with voltage application means tocomplete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the polystyrene-based electrophoretic particles 13,14 and 15 of respective colors were positively charged in the siliconeoil 1, the colored particles were moved to positions above the firstelectrodes 8 to provide respective color display states when the firstelectrodes 8 were supplied with −50 volts.

On the other hand, when the second electrodes 7 were supplied with −50volts, the colored particles 13, 14 and 15 were moved to above thesecond electrodes 7, the first electrodes 8 could be observed throughthe transparent insulating liquid 1 to provide a white display state.The response speed was 30 msec or shorter, and no display irregularitydue to localization of the colored particles was observed. Further, bycollecting the respective colored particles 2 above the first electrodes8 at selected tubes 3, the respective colors of yellow (Y), magenta (M)and cyan (C) could be selectively exhibited to allow a color display.

EXAMPLE 17

A display device was prepared in the following manner through a processas illustrated in FIGS. 31A-3F.

Tubes 3 (already provided with inner wall projections 3 a) each havingan inner diameter of 100 μm were filled with a display medium comprisingthe transparent insulating liquid 1 and white particles 2 of titaniumoxide, otherwise in the same manner as in Example 13.

Separately, a light-transmissive first substrate 4 of 200 μm-thick PETfilm was provided with first electrodes 8 of ITO stripes (FIG. 31A) andan insulating layer 5 of colored transparent polyimide. Further, on theinsulating layer 5, a dark black titanium carbonate film was formed andpatterned into second electrodes 7 of 30 μm-wide stripes extendingperpendicularly to the stripes of first electrodes 8.

Then, color layers 17 (Y), 18 (M) and 19 (C, not shown) were formed injuxtaposition with the second electrodes 7, and further coated with anupper half of insulating liquid 5 (FIG. 31C). By using the thus-treatedfirst substrate 4, a display device having a structure as shown in FIG.31F was prepared through steps as shown in FIGS. 31D to 31F otherwise inthe same manner as in Example 13.

The thus-prepared display device was driven by application of ±60 volts.The colored particles 2 of titanium oxide was negatively charged in theinsulating liquid 1 of silicone oil. As a result, the white particles 2were collected above the first electrodes 8 to provide a white displaystate when the first electrodes 8 were supplied with +60 volts.

On the other hand, when the second electrodes 7 were supplied with +60volts, the white particles 2 were collected above the second electrodes,so that the colored layers 17 and 18 (and 19) could be observed throughthe second substrate 6. The response speed was 30 msec or shorter, andno display irregularity due to localization of the colored particles 2was observed. By forming three types colored layers (17, 18, . . . ) ofyellow, cyan and magenta, a color display could be performed.

Further, when the display device was driven at a shorter voltageapplication period of 5 msec, the reflected light of respective colorscould be lowered to nearly a half. Thus, a multi-level gradationaldisplay could be performed by selecting various voltage applicationperiods, thus providing a color display device capable of gradationaldisplay.

EXAMPLE 18

A display device was prepared through similar steps as in Example 13 byusing tubes 3 having an inner diameter of 30 μm, colored particles ofca. 0.5-1.0 μm and second electrodes 7 in a smaller width of 10 μm.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using narrower secondelectrodes 7, the response time could be reduced to 5 msec or shorterwith no display irregularity due to localization of the coloredelectrophoretic particles.

According to this embodiment, similar performances as in Firstembodiment are attained except that the localization of electrophoreticparticles 2 is better suppressed due to obstruction of the movement ofthe particles in a longitudinal direction of each tube 3.

Fourth Embodiment

FIG. 32 is a perspective view of an electrophoretic display deviceaccording to an embodiment of the present invention, and FIGS. 33A and33B are partial sectional views thereof for illustrating an operationprinciple thereof.

This embodiment is different from Third embodiment described withreference to FIGS. 21 to 31 in that light-transmissive second electrodes7 are formed on a second substrate 6 (FIGS. 32 and 33) instead of afirst substrate 4. The other features are substantially identical tothose in Third embodiment.

As a result, this embodiment is different from First embodimentdescribed with reference to FIGS. 1 to 12 in the above-described pointand in that each tube 3 is provided with a plurality of projections 3 afrom the inner wall thereof at prescribed intervals for obstructing themovement of colored electrophoretic particles 2 in a longitudinaldirection thereof. The other features are substantially identical tothose in First embodiment.

As a result, this embodiment provides combined features of Secondembodiment and Third embodiment compared with First embodiment.

Thus, the display device according to this embodiment is operated insimilar manners as in Second embodiment as illustrated in FIGS. 32-36corresponding to FIGS. 15-18 for Second embodiment, and may be producedthrough processes as illustrated in FIGS. 37 and 38 corresponding toFIGS. 19 and 20 for Second embodiment, i.e., in similar manners as inFirst embodiment with appropriate modifications described with respectto Second and Third embodiments.

Some specific examples according to this embodiment will be describedbelow.

EXAMPLE 19

A display device was prepared through a process as illustrated in FIGS.8A and 37A-37F.

A cylindrical light-transmissive tube 3 of PET having an inner diameterof 200 μm was locally periodically heated by causing heat shrinkage tobe provided with inner wall projections 3 a at a pitch of 180 μmproviding constricted inner wall diameters of 100-150 μm. The tube 3 wasthen filled with a display medium comprising a white opaque insulatingliquid 1 of silicone oil dyed with oil-soluble white dye and blackelectrophoretic particles 2 of a polystyrene-carbon mixture havingparticle sizes of ca. 1-2 μm in a manner as illustrate in FIG. 8A, i.e.,by dipping one end of the tube 3 into a bath of the display medium undersufficient stirring in a vessel 21 and sucking from the other end of thetube 3. After the filling, both ends of the tube 3 were sealed up byheating.

Then, on a light-transmissive first substrate 4 of 200 μm-thick PETfilm, a titanium film was formed and patterned into first electrodes 8in the form of stripes (only one thereof being shown in FIG. 37A).Separately, on a light-transmissive second substrate 6 of 200 μm-thickPET film, an ITO film was formed and patterned into second electrodes 7in the form of stripes (FIG. 37B).

Then, on the first substrate 4 having a structure as shown in FIG. 37B,a plurality of the above-prepared tubes 3 provided with the inner wallprojections 3 a (not shown in FIG. 37C) and filled with the displaymedium of the white insulating liquid 1 and the black electrophoreticparticles 2 were arranged so that their extending directions wereperpendicular to the extension direction of the first electrodes 8 (FIG.37C). Then, the light-transmissive second substrate 6 provided with thesecond electrodes 7 was disposed above the tubes 3 (FIG. 37D), and thesubstrates 4 and 6 were bonded to each other with an ultraviolet-curableacrylic resin under a slight pressure between the substrates 4 and 6.

As a result, the upper and lower parts of the tubes 3 were made flat bycontact with the substrates 6 and 4, and the tubes 3 were disposed inintimate contact with each other, i.e., with no gap between each other(FIG. 37E). Along with the deformation of the tubes 3, the verticaldistance between the upper and lower portions of each inner wallprojection 3 a was narrowed to provide moving spaces S within which themovement of the electrophoretic particles 2 were substantially confinedto form a structure as shown in FIG. 37F (and also in FIG. 37E).Further, the structure was provided with a voltage application means tocomplete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for a display to be observed from the second substrate 6 side.As a result, as the black electrophoretic particles 2 were positivelycharged in the silicone oil 1, the particles 2 were moved to positionsabove the first electrodes 8 when the first electrodes 8 were suppliedwith −50 volts, thus providing a white display state (FIG. 33A).

On the other hand, when the second electrodes 7 were supplied with −50volts, the black particles 2 were collected on the second electrodes 7so that the display device exhibited a black display state (FIG. 33B).The response speed was 30 msec or shorter. No display irregularity dueto localization of the colored particles 2 was observed.

EXAMPLE 20

A display device was prepared through a process as illustrated in FIGS.8B and 38A-38E.

Cylindrical tube 3 of 200 μm in diameter not provided with inner wallprojections were each provided with maximum 30 μm-high projections 9 aalong an external side thereof at a longitudinal pitch of 300 μm (asshown in FIG. 38C). Then, the tubes 3 were filled with the same displaymedium comprising the white insulating liquid 1 and black coloredparticles 2 as used in Example 19 in a manner as illustrated in FIG. 8B,i.e., by dipping one end of each tube 3 containing the blackelectrophoretic particles 2 uniformly attached to the inner wall thereofinto a bath 21 of the white insulating liquid 1 and introducing thewhite insulating liquid 1 by sucking from the other end of the tube 3.After the filling, both ends of each tube 3 were sealed by heating.

Separately, first electrodes 8 were formed on a first substrate 4 (FIG.38A), and second electrodes 7 were formed on a second substrate 6 (FIG.38B), respectively, in the same manner as in Example 19. Further, theabove-prepared tubes 3 filled with the display medium and provided withexternal projections 9 a were arranged on the first substrate 4 providedwith first electrodes 8 with their extension directions perpendicular tothe stripe first electrodes 8 (FIG. 38C).

Thereafter, the second substrate 6 provided with the second electrodes 7was disposed above the tubes 3 so that the first electrodes 8 and secondelectrodes 7 were perpendicular to each other (FIG. 38D), and thesubstrates 4 and 6 were bonded to each other in the same manner as inExample 19 to form a structure shown in FIG. 38E. Thus, the tubes 3 weredisposed in intimate contact with each other and with their upper andlower surfaces made flat and in intimate contact with the secondsubstrate 6 and the first substrate 4. At the same time, each tube 3 wasprovided with inner wall projections 3 a by pressing with the externalprojections 9 a of an adjacent tube 3 to form a structure shown in FIG.38E. The structure was then provided with voltage application means tocomplete a display device.

The thus-prepared display device was driven by application of ±50 voltsbetween the electrodes in the same manner as in Example 19, whereby adisplay with no display irregularity due to localization of the coloredparticles was performed at a response speed of 30 msec or shorter.

EXAMPLE 21

A display device was produced in the following manner through a processas illustrated in FIGS. 37A-37F.

First of all, cylindrical light-transmissive tubes 3 of PET having aninner diameter of 200 μm provided with inner wall projections 3 a bylocally periodical heating at a pitch of 200 μm and were filled withthree colors of display media comprising three colors of transparentinsulating liquid 1 of silicone oil dyed in yellow (Y), magenta (M) andcyan (C), respectively, and white electrophoretic particles 2 oftitanium oxide fine powder having particle sizes of ca. 1-2 μm. Afterthe filling, both ends of each tube 3 were sealed by heating. Thus threetypes of tubes 3 containing three colors of insulating liquid 1 wereprepared.

Separately, a first substrate 4 was provided with first electrodes 8,and second electrodes 7 were formed on a second substrate 6, as shown inFIGS. 37A-37B, in the same manner as in Example 19.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions perpendicular to the extension directionof the first electrodes 8 on the first substrate 4 (FIG. 37C).Thereafter, the second substrate 6 having thereon the second electrodes7 was disposed thereabove so that the first electrodes 8 and the secondelectrodes 7 were perpendicular to each other (FIG. 37D), and thesubstrates 4 and 6 were bonded to each other in the same manner as inExample 19 to form a structure shown in FIG. 37E. At this time, theupper and lower portions of each projection 3 a were made closer to eachother to form a structure as shown in FIG. 37F having moving sections S.The structure was then provided with voltage application means tocomplete a display device.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the white electrophoretic particles 2 of titaniumoxide were negatively charged in the silicone oil 1, the white particles2 were moved to positions above the first electrodes 8 to displayrespective colors of the three types of the insulating liquid 1 when thefirst electrodes 8 were supplied with +50 volts (FIG. 35).

On the other hand, when the second electrodes 7 were supplied with +50volts, the white particles 2 were moved to above the second electrodes7, a white display state was exhibited. The response speed was 30 msecor shorter, and no display irregularity due to localization of thecolored particles was observed. Further, by collecting the coloredparticles 2 above the first electrodes 8 at selected tubes 3, therespective colors of yellow (Y), magenta (M) and cyan (C) could beselectively exhibited to allow a color display.

EXAMPLE 22

A display device was produced in the following manner through a processas illustrated in FIG. 8B and FIGS. 37A-37F.

First of all, cylindrical light-transmissive tubes 3 of PET each havingan inner diameter of 200 μm were filled with three colors of displaymedia comprising a white insulating layer 1 of silicone oil dyed withoil-soluble white dye and three colors of electrophoretic particles 2comprising mixtures of polystyrene and colorants of yellow (Y), magenta(M) and cyan (C), respectively, and having particle sizes of ca. 1-2 μm.

The three types of tubes 3 were each prepared through a filling processas illustrated in FIG. 8B, and were further provided with inner wallprojections 3 a at a pitch of 200 μm.

Separately, first electrodes 8 were formed on a first substrate 4 (FIG.37A), and second electrodes 7 were formed on a second substrate 6 (FIG.37B), respectively, in the same manner as in Example 19.

Then, the above-prepared three colors of tubes 3 were arranged withtheir longitudinal directions perpendicular to the extension directionof the first electrodes 8 (FIG. 37C). Thereafter, the second substrate 6provided with the second electrodes 7 was disposed above the firstsubstrate 4 (FIG. 37D), so that the first electrodes 8 and the secondelectrodes 7 were perpendicular to each other, and the substrates 4 and6 were bonded to each other in the same manner as in Example 19 to forma structure shown in FIG. 37E. At this time, the upper and lowerportions of each projection 3 a were made closer to each other to form astructure a shown in FIG. 37F having moving sections S. The structurewas then provided with voltage application means to complete a displaydevice.

The thus-prepared display device was driven by application of ±50 volts.As a result, since the polystyrene-based electrophoretic particles 13,14 and 15 of respective colors were positively charged in the siliconeoil 1, the colored particles were moved to positions above the firstelectrodes 8 to provide a white display state due to the color of thewhite insulating liquid 1 when the first electrodes 8 were supplied with−50 volts (FIG. 36).

On the other hand, when the second electrodes 7 were supplied with −50volts, the colored particles 13, 14 and 15 were moved to above thesecond electrodes 7, the respective colors of the colored particles13(Y), 14(M) and 15(C) were observed. The response speed was 30 msec orshorter, and no display irregularity due to localization of the coloredparticles was observed. Further, by collecting the respective coloredparticles 2 above the second electrodes 7 at selected tubes 3, therespective colors of yellow (Y), magenta (M) and cyan (C) could beselectively exhibited to allow a color display.

EXAMPLE 23

A display device was prepared through similar steps as in Example 19 byusing tubes 3 having an inner diameter of 30 μm, colored particles ofca. 0.5-1.0 μm and a smaller gap of 25 μm between the substrates 4 and6.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using the smaller gap, theresponse time could be reduced to 5 msec or shorter with no displayirregularity due to localization of the colored electrophoreticparticles.

According to this embodiment, in addition to the effects of Firstembodiment, it is possible to attain the effect of allowing a displaybased on vertical movement of electrophoretic particles 2 and also theeffect of reducing the localization of the electrophoretic particles 2due to suppression of movement thereof in a longitudinal direction oftubes by provision of inner wall projections.

Fifth Embodiment

FIG. 39 is a schematic perspective view of an electrophoretic displaydevice according to this embodiment, and FIGS. 40A and 40B are partialsectional views thereof for illustrating an operation principle thereof.

This embodiment is structurally similar as Second embodiment in thatmutually intersecting first electrodes 8 and second electrodes 7respectively in the form of stripes are disposed close to firstsubstrate 4 and a second substrate 6, respectively, for allowing anelectrophoretic display by movement of electrophoretic particles 2vertically to the substrates. In this embodiment, however, each firstelectrode 8 is disposed along a tube 3 filled with a display medium, andthe second electrodes 7 are disposed on the second substrate 6 so as tocontact the tubes 3, optionally via electroconductive films 90 formed inadvance on the tubes 3, for ensuring the vertical movement between theopposing parts of the first electrodes 8 and second electrodes 7 formingpixels between the first substrate 4 and second electrode 6.

More specifically, the display device shown in FIGS. 39 and 40 includesa plurality of light-transmissive tubes 3 filled with a display mediumDM comprising an insulating liquid 1 and electrophoretic articles 2 anddisposed between a first substrate 4 and a second substrate 6. Along anexternal side wall of each light-transmissive tube 3, a stripe-formfirst electrode 8 is disposed and stripe-form second electrodes 7 aredisposed on the second substrate 6 so as to perpendicularly intersectthe first electrodes 8, thereby forming a matrix electrode structure fordriving a matrix of pixels each composed of the display medium DM and apair of the opposing first electrode 8 and second electrode 7sandwiching the display medium.

The first electrodes 8 are disposed in contact with the first substrate4. The parts on the tube 3 contact with the second electrodes 7 may beprovided with electroconductive films 90 so as to improve an electricalcontact between the films 90 and the second electrodes 7 and therebyensure the movement of the electrophoretic particles 2.

In this embodiment, a pair of first electrode 8 and second electrode 7are disposed opposite to each other, so that the electrophoreticparticles 2 are moved between the electrodes vertically to thesubstrates 4 and 6 to effect an electrophoretic display. For example, ifthe electrophoretic particles 2 are collected on the first electrodes 8by voltage application between the first electrodes 8 and the secondelectrodes 7, the color of the insulating liquid 1 is observed to aviewer on the second substrate 6 side as shown in FIG. 40A. On the otherhand, if the electrophoretic particles 2 are collected on the secondelectrodes 7 by application of a reverse polarity-voltage, the color ofthe particles 2 is observed to the viewer. As a result, if the particles2 are colored in black and the insulating liquid 1 is colored in white,a white-black binary display becomes possible.

Depending on selection of the viewer's side, the second substrate 6 andsecond electrodes 7 thereon are made light-transmissive as shown inFIGS. 40A and 40B, or the first substrate 4 and first electrodes 8thereon are made light-transmissive if the device is observed from thefirst substrate 4 side.

By using plural colors of insulating liquid 1 and/or electrophoreticparticles 2, a color display may be possible similarly as in Secondembodiment.

The display device shown in FIGS. 39 and 40 may be produced in thefollowing manner through a process as illustrated in FIGS. 41A-41D,FIGS. 42A-42D and FIG. 8A or 8B.

First of all, a first electrode 8 of a stripe form in a prescribed widthis formed along a generatrix of a cylindrical tube 3 as shown in FIGS.41A (perspective view) and 41B (sectional view). It is preferred thatthe tube 3 is further provided with electroconductive films 90 at partsthereof contacting the second electrodes 7 along a side opposite to thefirst electrode 8 as shown in FIGS. 41C (perspective view) and 41D(sectional view). The width of the first electrode 8 and the sizes ofthe films 90 may be determined depending on the prescribed pixel size inconsideration of the tube 3 diameter.

The tube 3 may have a shape of a cylinder (as shown in FIGS. 41A-41B) ora rectangle (as incorporated in the device of FIGS. 39-40) and comprisea material selected as described with reference to First embodiment.

The first electrode 8 and electroconductive films 9 formed on the tube 3may comprise a metal, such as Al, Au, Pt, Ag, Ni, Ti or Cr, or atransparent metal oxide, such as ITO (indium tin oxide), ZnO or SnO₂,for providing transparent electroconductive films, and may be formed onthe tube 3 by vacuum evaporation, sputtering, ion plating, etc.,followed by patterning, e.g., by photolithography, as desired.

The tube 3 provided with the first electrode 8 and electroconductivefilms 90 may be filled with the display medium DM in the same manner asin First embodiment described with reference to FIGS. 8A and 8B. Uniformdistribution within a tube 3 and uniform attachment onto the inner wallthereof of the electrophoretic particles 2 may be assisted if a voltageis applied to the first electrode 8 during the filling step. The displaymedium DM may comprise an insulating liquid 1 and coloredelectrophoretic particles 2 similar to those described with reference toFirst embodiment.

Instead of the above-mentioned sequence of formation of the firstelectrode 8 and the electroconductive films 9 on the tube 3, followed byfilling of the tube 3 with the display medium, it is possible to firsteffect the filling of the tube 3 with the display medium, followed byformation of the electrode 8 and the films 90 on the tube 3.

By using a plurality of the above-prepared tubes 3 provided with thefirst electrode 8 and the electroconductive films 90 and filled with thedisplay medium DM, a display device as shown in FIGS. 39 and 40 may beproduced in the following manner through a process as illustrated inFIGS. 42A-42D.

First, a second substrate 6 is provided with stripe second electrodes 7as shown in FIG. 42A similarly as the formation of the first electrodes8 on the first substrate 4 in FIG. 9A for First embodiment.

Then, as shown in FIG. 42B, the above-prepared tubes 3 filled with thedisplay medium DM are arranged on a first substrate 4 so that the firstelectrodes 8 formed thereon contact the first substrate 4. As desired, asupporting member composed of, e.g., silicone resin or acrylic resin maybe disposed between adjacent tubes 3 or between a tube 3 and a firstsubstrate 4 or a second substrate 6.

In the case of color display, the tubes 3 containing different colors ofdisplay medium DM as by inclusion of different colors of electrophoreticparticles 2 or different colors of insulating liquid 1 may be arrangedin a prescribed order, e.g., an order of yellow (Y), magenta (M) andcyan (C).

Then, as shown in FIG. 42C, the second substrate 6 provided with thesecond electrodes 7 is disposed above and in alignment with the tubes 3so that the first electrodes 8 on the tubes 3 and the second electrodes7 on the second substrate 6 are perpendicular to each other. Then, byhardening the above-mentioned supporting member (not shown) of siliconeresin or acrylic resin, if used, or/and by hardening a photocurable orheat-curable adhesive (not shown) applied at a peripheral part of thestructure shown in FIG. 42C, the first substrate 4 and the secondsubstrate 6 are bonded to each other under a slight pressure. At thistime, the tubes 3 are deformed corresponding to a set spacing betweenthe substrates 4 and 6, whereby the tubes 3 are disposed in intimatecontact with each other to form a structure shown in FIG. 42D.(Incidentally, in case where the tubes 3 are formed of a material withlittle deformability, the tubes 3 may be provided with a sectional shapeas shown in FIG. 42D prior to the bonding step shown in FIG. 42C as willbe described with reference to FIGS. 43A-43D for an example hereinafter.The use of such tubes 3 having a rectangular section may facilitate thearrangement of the tubes 3 on the first substrate 4.)

Finally, the structure shown in FIG. 42D is provided with a means (notshown) for applying voltages between the first electrodes 8 and thesecond electrodes to complete a display device as shown in FIGS. 39 and40.

According to this embodiment, in addition to the effects attained inSecond embodiment, it is possible to reduce a positional deviationbetween the opposing first electrodes 8 and second electrodes 7, thusreducing a display irregularity caused by such a positional deviation.

Some specific examples according to this embodiment will be describedhereinbelow.

EXAMPLE 24

A display device was produced in the following manner through a processas illustrated in FIGS. 42A-42D.

On an outer surface of and along a longitudinal generatrix of a 10μm-thick light-transmissive cylindrical tube 3 of PET having an innerdiameter of 200 μm, a 300 nm-thick and 150 μm-wide stripe of Al firstelectrode 8 was formed by vacuum evaporation.

The tube 3 was then filled with a display medium DM comprising a whiteinsulating liquid 1 of silicone oil dyed with an oil-soluble white dyeand 3 wt. % of black electrophoretic particles 2 of a polystyrene-carbonmixture having particle sizes of 1-2 μm in a manner as illustrated inFIG. 8A, i.e., by dipping one end of the tube 3 into a bath of thedisplay medium DM under sufficient stirring in a vessel 21 and suckingfrom the other end of the tube 3. After the filling, both ends of thetube 3 were sealed up by heating.

Separately, on a light-transmissive second substrate 6 of 200 μm-thickPET film, a 300 nm-thick ITO film was formed and patterned byphotolithography including dry etching to form second electrodes 7 of150 μm-wide stripes at a pitch of 200 μm (FIG. 42A).

Then, a plurality of the above-prepared tubes 3 each provided with afirst electrode 8 and filled with the display medium DM were arranged ona first substrate 4 of 200 μm-thick PET film so that the firstelectrodes 8 thereon contacted the first substrate 4 (FIG. 42B but withno film 90).

Then, the above-prepared second substrate 6 provided with the secondelectrodes 7 (FIG. 42A) was placed on the tubes 3 so that the secondelectrodes 7 contacted the tubes 3 and the second electrodes 7 wereperpendicular to the second electrodes 8 and the second substrate 6 waspositionally aligned with the first substrate 4 (FIG. 42C). Further, acasting polypropylene-type heat-curable adhesive was applied between thesubstrates at peripheries of the stacked structure, which was theninstalled within a PET-made outer frame (not shown) and heated at 100°C. via the outer frame while setting a gap between the substrates 4 and6 at 140 μm. As a result, the upper and lower parts of the tubes 3 weremade flat by contact with the substrates 6 and 4, the tubes 3 weredisposed in intimate contact with each other to produce a structure asshown in FIG. 42D (but with no films 90). Further, the structure wasprovided with a voltage application means to provide a display device.

The thus-prepared display device was subjected to a display operation tobe observed from the second substrate 6 side by voltage application of±50 volts between the first and second electrodes 8 and 7. In thisexample, the black particles 2 were positively charged in the insulatingliquid 1 of silicone oil and moved toward an electrode supplied with anegative voltage. As a result, the black particles 2 were moved to thefirst electrodes 8 to provide a white display state when the firstelectrodes were supplied with −50 volts (FIG. 40A). On the other hand,the black particles 2 were moved to the second electrodes 7 to provide ablack display state when the second electrodes 7 were supplied with −50volts (FIG. 40B). The response time was 30 msec or shorter. No displayirregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 25

A display device was prepared in the same manner as in Example 24 exceptfor using a display medium DM comprising a blue insulating liquid 1formed by dissolving oil-soluble dye in silicone oil and 3 wt. % whiteparticles 2 of TiO₂ having particle sizes of 1-2 μm.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a blue display statewhen the first electrodes were supplied with +50 volts and moved to thesecond electrodes 7 to provide a white display state when the secondelectrodes 7 were supplied with +50 volts. The response time was 30 msecor shorter, and no display irregularity due to localization of thecolored particles 2 was observed.

EXAMPLE 26

A display device was prepared in the same manner as in Example 24 exceptfor forming the first electrode 8 as a 300 nm-thick ITO stripe film bysputtering on the tube 3 and forming the second electrodes 7 of 300nm-thick Ag films on the second substrate 6.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As the blackparticles 2 were positively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a white display statewhen the first electrodes were supplied with −50 volts and moved to thesecond electrodes 7 to provide a black display state when the secondelectrodes 7 were supplied with −50 volts. The response time was 30 msecor shorter, and no display irregularity due to localization of thecolored particles 2 was observed.

EXAMPLE 27

A display device was produced in the following manner through a processas illustrated in FIGS. 43A-43C.

On an outer side in a longitudinal direction of a light-transmissivetube 3 of 10 μm-thick PET film having a square section of 200 μm×200 μmwith round corners, a 300 nm-thick and 150 μm-wide stripe of Al firstelectrode 8 was formed by vacuum evaporation. Further, on the oppositeside of the tube 3 with respect to the Al electrode side, 300 nm-thickITO films 90 of 150×150 μm-square were formed at a pitch of 200 μm alonga longitudinal direction of the tube 3.

The tube 3 was filled with the same display medium DM as used in Example24, and a plurality of the tubes 3 thus prepared were arranged incontact with each other on the same first substrate 4 as in Example 24(FIG. 43B). Further thereon, the same second electrode 6 provided withsecond substrates 7 as in Example 24 (FIG. 43A) was placed so that thesecond substrates 7 contacted the ITO films 90 formed on the tubes 3.Further, the stacked structure after alignment of the substrates 4 and 6and application of an adhesive was installed within an outer frame andheated for bonding of the substrates in the same manner as in Example 24to provide a structure as shown in FIG. 43C. The structure was furtherprovided with a voltage application means to complete a display device.

The thus-prepared display device was subjected to a display operation inthe same manner as in Example 24, whereby a good display free fromdisplay irregularity due to localization of the colored particles 2 wasperformed at a response time of 30 msec or shorter.

EXAMPLE 28

A display device was produced in the following manner through a processas illustrated in FIGS. 42A-42D.

On an outer surface of and along a longitudinal generatrix of a 10μm-thick light-transmissive cylindrical tube 3 of PES having an innerdiameter of 200 μm, a 300 nm-thick and 100 μm-wide stripe of ITO firstelectrode 8 was formed.

A plurality of tubes 3 thus-treated were then filled with three colorsof display media DM comprising three colors of insulating liquid 1 ofsilicone oil dyed with oil-soluble dyes of yellow, magenta and cyan,respectively, and 3 wt. % of white electrophoretic particles 2 oftitanium oxide having particle sizes of 1-2 μm in a manner asillustrated in FIG. 8B, i.e., by dipping one end of each tube 3containing white electrophoretic particles 2 uniformly attached to theinner wall thereof into a bath of insulating liquid 1 dyed in aprescribed color and introducing the colored insulating liquid 1 bysucking from the other end of the tube 3. After the filling, both endsof each tube 3 were sealed by heating. Thus three types of tubes 3containing three colors of insulating liquid 1 were prepared.

Separately, on a light-transmissive second substrate 6 of 200 μm-thickPET film, a 300 nm-thick ITO film was formed and patterned byphotolithography including dry etching to form second electrodes 7 of150 μm-wide stripes at a pitch of 200 μm (FIG. 42A).

Then, the above-prepared three colors of tubes 3 each also provided witha first electrode 8 were arranged in a prescribed order on a firstsubstrate 4 of 200 μm-thick PET film so that the first electrodes 8thereon contacted the first substrate 4 (FIG. 42B but with no film 90).

Then, the above-prepared second substrate 6 provided with the secondelectrodes 7 (FIG. 42A) was placed on and in alignment with theabove-prepared first substrate 4 on which the tubes 3 were arranged, andthe substrates 4 and 6 were bonded to each other in the same manner asin Example 24 to provide a structure as shown in FIG. 42D (but with nofilm 90), which was then provided with a voltage application means tocomplete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to display the respective colorsof the insulating liquids when the first electrodes were supplied with+50 volt and moved to the second electrodes 7 to provide a white displaystate when the second electrodes 7 were supplied with +50 volts.Accordingly, by changing a combination of voltages applied to the firstelectrode 8 and the second electrode 7 at respective pixels, a colordisplay could be performed as combinations of yellow, magenta and cyan.The response time was 30 msec or shorter, and no display irregularitydue to localization of the colored particles 2 was observed.

EXAMPLE 29

A display device was prepared in the same manner as in Example 28 exceptfor using three colors of display media comprising a white insulatingliquid 1 of dyed silicone oil and three colors of 1 to 2 μm-dia.electrophoretic particles 2 formed as mixtures of polystyrene and one ofyellow, magenta and cyan colorants.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As thecolored particles 2 were positively charged in the silicone oil 1, theparticles 2 were moved to the first electrodes 8 to display a whitedisplay state when the first electrodes were supplied with −50 volt andmoved to the second electrodes 7 to display the respective colors of thecolored particles 2 when the second electrodes 7 were supplied with −50volts. Accordingly, by changing a combination of voltages applied to thefirst electrode 8 and the second electrode 7 at respective pixels, acolor display could be performed as combinations of yellow, magenta andcyan. The response time was 30 msec or shorter, and no displayirregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 30

A display device was prepared through similar steps as in Example 24 byusing tubes 3 having an inner diameter of 30 μm, a smaller gap of 25 μmbetween the substrates 4 and 6, and colored particles of ca. 0.5-1.0 μm.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using a narrower gap, theresponse time could be reduced to 5 msec or shorter with no displayirregularity due to localization of the colored electrophoreticparticles.

According to this embodiment, similar effects as in Second embodimentcan be attained while simplifying the processing of the substrates.Further the possibility of positional deviation between the first andsecond electrodes is reduced to allow less display irregularity.

Sixth Embodiment

FIG. 44 is a schematic perspective view of an electrophoretic displaydevice according to this embodiment, and FIGS. 45A and 45B are partialsectional views thereof for illustrating an operation principle thereof.

This embodiment is different from Fifth embodiment in that the firstelectrodes 8 are disposed on the first substrate 4, and the secondelectrodes 7 are each disposed on the first substrate 4 side of andalong a longitudinal direction of one of the tubes 3 and extendperpendicularly to and in lamination with the first electrodes 8 via aninsulating layer 5 formed over the first electrodes 8.

In this embodiment, the first electrodes 8 and the second electrodes 7are both arranged close to the first substrate 4, and as a result ofvoltage application between these electrodes, the coloredelectrophoretic particles 2 are moved between these electrodes, i.e.,horizontally with respect or in parallel to the substrates 4 and 6 toeffect an electrophoretic display.

The display principle is substantially identical to the one explainedwith reference to First embodiment as illustrated in FIGS. 44 to 49corresponding to FIGS. 1 to 7 for First embodiment. For a better displayquality, a masking pattern 16 may be formed (FIG. 46), and for colordisplay, arbitrary color layers 17, 18 and 19 (FIGS. 47 and 48) may beformed, respectively, similarly as in First embodiment.

In order to ensure an electricity supply to the second electrodes 7formed on the tubes 4, it is possible to form an electroconductive films(not shown, like ones denoted by numeral 90 in figures for Fifthembodiment) on the first substrate 4 in a form insulated from the firstelectrodes 8. As the display device is driven by voltage supply to thefirst and second electrodes 8 and 7, the form and size of a secondelectrode 7 may be determined based on a balance with a first electrodefor a pixel concerned. The size of a second electrode 7 can be smalleror larger than a first electrode 8 for each pixel. The second electrode7 may have a width and a thickness appropriately determined based onspecification of a desired display device.

The display device according to this embodiment may be produced throughprocesses as illustrated in FIGS. 51-53 similarly as in Fifth embodimentexcept that a relatively narrow second electrode 7 (instead of a firstelectrode 8 is formed on a tube 3) (FIGS. 50A and 50B). It is alsopossible to form an insulating layer 5 a in advance on an outer side ofthe second electrodes 7 as shown in FIG. 50C at parts contacting thefirst electrodes 8 on the first substrate 4. The insulating layer 5 amay be formed of, e.g., a transparent insulating material capable offorming pinhole-free films, such as polyimide and polyethyleneterephthalate. The insulating layer 5 a is formed in order to prevent anelectrical connection between the first electrodes 8 on the firstsubstrate 4 and the second electrode 7 formed on an outer surface of thetube 3. Accordingly, the insulating layer 5 a can be formed around anentire circumference of the tube 3 while it can depend on other designfactors. Alternatively, such insulating layer 5 a may be omitted if aninsulating layer 5 is formed over the first electrodes 8 as shown inFIG. 44.

Further, in order to provide a display device as shown in FIG. 48provided with color layers 17 a, 18 a and 19 a, such a color layer 17 a(or 18 a or 19 a) may be disposed as a stripe parallel to a stripesecond electrode 7 on an outer surface of a tube 3 as shown in FIG. 50D.

The other features and materials for the respective members of thedisplay device according to this embodiment are similar to thosedescribed with reference to First and Fifth embodiments.

Some specific examples according to this embodiment will be describedbelow.

EXAMPLE 32

A display device having a structure as shown in FIGS. 44 and 45 wasproduced in the following manner through a process as illustrated inFIGS. 51A-51D.

On an outer surface of and along a longitudinal generatrix of a 10μm-thick light-transmissive cylindrical tube 3 of PET having an innerdiameter of 200 μm, a 300 nm-thick and 50 μm-wide stripe of Al secondelectrode 8 was formed by vacuum evaporation.

The tube 3 was then filled with a display medium DM comprising atransparent insulating liquid 1 of silicone oil and 3 wt. % of blackelectrophoretic particles 2 of a polystyrene-carbon mixture havingparticle sizes of 1-2 μm in a manner as illustrated in FIG. 8A. Afterthe filling, both ends of the tube 3 were sealed up by heating.

Separately, on a light-transmissive first substrate 4 of 200 μm-thickPET film, a 300 nm-thick ITO film was formed and patterned byphotolithography including dry etching to form second electrodes 8 of150 μm-wide stripes at a pitch of 200 μm, which were then coated with a30 μm-thick white insulating layer 5 of PET colored with TiO₂ fineparticles (FIG. 51A).

Then, a plurality of the above-prepared tubes 3 each provided with asecond electrode 7 and filled with the display medium DM were arrangedon the first substrate 4 so that the tubes 3 were perpendicular to thefirst electrodes 8 and the second electrodes 7 thereon contacted theinsulating layer 5 on the first substrate 4 (FIG. 51B).

Then, a second substrate 6 of 200 μm-thick PET film was placed on thetubes 3 and positionally aligned with the first substrate 4 (FIG. 51C).Further, a casting polypropylene-type heat-curable adhesive was appliedbetween the substrates at peripheries of the stacked structure, whichwas then installed within a PET-made outer frame (not shown) and heatedat 100° C. via the outer frame while setting a gap between thesubstrates 4 and 6 at 140 μm. As a result, the upper and lower parts ofthe tubes 3 were made flat by contact with the substrates 6 and 4, thetubes 3 were disposed in intimate contact with each other to produce astructure as shown in FIG. 51D. Further, the structure was provided witha voltage application means to provide a display device.

The thus-prepared display device was subjected to a display operation tobe observed from the second substrate 6 side by voltage application of±50 volts between the first and second electrodes 8 and 7. In thisexample, the black particles 2 were positively charged in the insulatingliquid 1 of silicone oil and moved toward an electrode supplied with anegative voltage. As a result, the black particles 2 were moved to thefirst electrodes 8 to provide a black display state when the firstelectrodes were supplied with −50 volts (FIG. 45A). On the other hand,the black particles 2 were moved to the second electrodes 7 to provide agrayish white display state when the second electrodes 7 were suppliedwith −50 volts (FIG. 45B). The response time was 30 msec or shorter. Nodisplay irregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 33

A display device was prepared though a process as illustrated in FIGS.52A-52D.

A PET tube 3 of 200 μm was provided with a 50 μm-wide second electrode 7of Al in the same manner as in Example 32 and the Al second electrode 7was further coated with a 5 μm-thick and 100 μm-wide insulating layer 5a of PET at a pitch of 200 μm along the length of the tube 3. The tube 3was then filled with the same display medium DM as used in Example 32.

Separately, a first substrate 4 identical to the one used in Example 32was provided with first electrodes 8 of ITO stripes (FIG. 52A) in thesame manner as in Example 32. Thereon, a plurality of theabove-processed tubes 3 were arranged so as to be perpendicular to thefirst electrodes 8 and so that the second electrodes 7 contacted thefirst substrate 4 via the insulating layer 5 a, and a second substrate 6identical to the one used in Example 32 was further disposed thereon(FIG. 52C). Thereafter, the structure was installed within an outerframe and subjected to bonding of the substrates 4 and 6, followed byprovision of a voltage application means, in the same manner as inExample 32.

The thus-prepared display device was subjected to a display byapplication of ±50 volts in the same manner as in Example 32, wherebygood display free from display irregularity due to localization of thecolored particles was performed at a response time of 30 msec orshorter.

EXAMPLE 34

A color display device having an organization as illustrated in FIGS.45A and 45B was prepared though a process as illustrated in FIGS.51A-51D.

A PES tube 3 of 200 μm was provided with a 50 μm-wide second electrode 7of Al in the same manner as in Example 32. A plurality of the tubes 3thus treated were then filled with three colors of display media DMcomprising three colors of silicone oil dyed with oil-soluble dyes ofyellow, magenta and cyan, respectively, and 3 wt. % of white particles 2of TiO₂ having particle sizes of 1-2 μm by a method as illustrated inFIG. 8B, whereby three types of tubes 3 containing three colors ofelectrophoretic particles 2 were prepared.

Separately, a first substrate 4 identical to the one used in Example 32was provided with 50 μm-wide first electrodes 8 of ITO stripes andfurther coated with a 5 μm-thick transparent polyimide layer 5 otherwisein the same manner as in Example 32. Thereon, the above-processed threecolors of tubes 3 were arranged so as to be perpendicular to the firstelectrodes 8 and so that the second electrodes 7 contacted theinsulating layer 5 on the first substrate 4 (FIG. 51B), and a secondsubstrate 6 identical to the one used in Example 32 was further disposedthereon (FIG. 51C). Thereafter, the structure was installed within anouter frame and subjected to bonding of the substrates 4 and 6, followedby provision of a voltage application means, in the same manner as inExample 32.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the first substrate 4 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a white display statewhen the first electrodes were supplied with +50 volt and moved to thesecond electrodes 7 to display the respective colors of the coloredinsulating liquids 1 when the second electrodes 7 were supplied with +50volts. Accordingly, by changing a combination of voltages applied to thefirst electrode 8 and the second electrode 7 at respective pixels, acolor display could be performed as combinations of yellow, magenta andcyan. The response time was 30 msec or shorter, and no displayirregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 35

A color display device having an organization as illustrated in FIG. 46was prepared through a process similar to the one illustrated in FIGS.51A-51D.

Three colors of display media DM were prepared as mixtures of aninsulating liquid 1 of silicone oil and 1 to 2 μm-dia. colored particlescomprising polystyrene in mixture with colorants of yellow, magenta andcyan, respectively. A plurality of tubes 3 each provided with a secondelectrode 7 were separately filled with the above three colors ofdisplay media DM otherwise in the same manner as in Example 33 toprepare three types of tubes.

Separately, a first substrate 4 of 200 μm-thick PET film was coated witha white layer containing TiO₂ particles (not shown), and furtherprovided thereon with first electrodes 8 of 300 nm-thick and 150 μm-wideITO stripes at a pitch of 200 μm and a 5 μm-thick transparent polyimideinsulating layer 5 (close to FIG. 51A).

On the thus-processed first substrate 4, the above-prepared three colorsof the tubes 3 each provided with a second electrode 7 were arranged ina prescribed order so that the second electrodes 7 thereon wereperpendicular to the first electrodes 8 and contacted the insulationlayer 5 on the first substrate 4 (FIG. 51B).

Separately, on a second substrate 6 of 200 μm-thick PET film, a darkblack-colored 300 nm-thick titanium carbide film was formed andpatterned by photolithography including dry etching to form maskingstripes 16 (FIG. 46) corresponding to second electrodes 7. Thethus-treated second substrate 6 was disposed on the tubes 3 arranged onthe first substrate 4 with the masking stripes 16 downward so as to bealigned with the second electrodes 7 after deformation of the tubes 3(close to FIG. 51C). Then, the structure was installed within an outerframe, bonding of the substrates and provision of a voltage applicationmeans in the same manner as in Example 32 to complete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As thecolored particles 2 were positively charged in the silicone oil 1, theparticles 2 were moved to the first electrodes 8 to display therespective colors of the colored particles 2 when the first electrodeswere supplied with −50 volt and moved to the second electrodes 7 todisplay a white color of the first electrodes 8 when the secondelectrodes 7 were supplied with +50 volts. Accordingly, by changing acombination of voltages applied to the first electrode 8 and the secondelectrode 7 at respective pixels, a color display could be performed ascombinations of yellow, magenta and cyan. The response time was 30 msecor shorter, and no display irregularity due to localization of thecolored particles 2 was observed.

EXAMPLE 36

A color display having an organization of FIG. 47 was prepared through aprocess as illustrated in FIGS. 53A-53D.

Tubes 3 each provided a second electrode 7 and filled with a displaymedium were formed in the same manner as in Example 32 except for usinga display medium comprising a insulating liquid 1 of silicone oil and 3wt. % of 1 to 2 μm-dia. white colored particles 2 of TiO₂.

Separately, a first substrate 4 identical to the one used in Example 32was provided with stripe first electrodes 8 of ITO and coated with a 5μm-thick transparent polyimide layer (as a lower half of 5), on whichcolored layers 17, 18 and 19 of yellow, magenta and cyan respectively inthe form of stripes were formed in a prescribed order and so as toextend perpendicularly to the first electrodes 8 and then further coatedwith a 5 μm-thick transparent polyimide layer (upper half of 5), therebyproviding a structure of processed first substrate 4 as shown in FIG.53A.

Then, the above-prepared tubes 3 each provided with a second electrode 7and filled with a display medium were arranged on the above-processedfirst substrate 4 so that each second electrodes 7 thereon was parallelto the color stripes 17 (18, 19) and disposed between adjacent colorstripes 17 (18, 19) (FIG. 53B).

Then, a second substrate 6 identical to the one used in Example 32 wasplaced thereover (FIG. 53C), and the structure was installed within anouter frame, bonding of the substrates 4 and 6, and provision of avoltage application means in the same manner as in Example 32 to providea display device having a structure as shown in FIG. 47 (FIG. 53D).

The thus-prepared display device was subjected to voltage application of±60 volts for observation from the second substrate 6 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a white display state(as shown in FIG. 47) when the first electrodes were supplied with +60volt and moved to the second electrodes 7 to display the respectivecolors of the color layers 17, 18 and 19 when the second electrodes 7were supplied with +50 volts. Accordingly, by changing a combination ofvoltages applied to the first electrode 8 and the second electrode 7 atrespective pixels, a color display could be performed as combinations ofyellow, magenta and cyan. The response time was 30 msec or shorter, andno display irregularity due to localization of the colored particles 2was observed.

EXAMPLE 37

A color display device having an organization as shown in FIG. 48 wasprepared through a process as illustrated in FIGS. 54A-54D.

Three tubes 3 each provided with a second electrode 7 similarly as inExample 32 were further provided with one of three color layers 17 a(yellow), 18 a (magenta) and 19 a (cyan), respectively. Thethus-obtained three colors of tubes 3 were further filled with the samedisplay medium as in Example 36 comprising a transparent insulatingliquid 1 of insulating liquid 1 and white colored particles 2.

Separately, a first substrate 4 identical to the one used in Example 32was provided with stripe first electrodes 8 and a transparent insulatinglayer 5 (FIG. 54A) in the same manner as in Example 32. Theabove-prepared three colors of tubes 3 were arranged thereon in aprescribed order of color layers 17 a, 18 a and 19 a (FIG. 54B), asecond substrate 6 identical to the one used in Example 32 was placedthereover (FIG. 54C), and the structure was installed within an outerframe, bonding of the substrates 4 and 6, and provision of a voltageapplication means in the same manner as in Example 32 to provide adisplay device having a structure as shown in FIG. 48 (FIG. 54D).

The thus-prepared display device was subjected to voltage application of±60 volts for observation from the second substrate 6 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a white display state(as shown in FIG. 48) when the first electrodes were supplied with +60volt and moved to the second electrodes 7 to display the respectivecolors of the color layers 17 a, 18 a and 19 a) when the secondelectrodes 7 were supplied with +60 volts. Accordingly, by changing acombination of voltages applied to the first electrode 8 and the secondelectrode 7 at respective pixels, a color display could be performed ascombinations of yellow, magenta and cyan. The response time was 30 msecor shorter, and no display irregularity due to localization of thecolored particles 2 was observed.

EXAMPLE 38

A display device was prepared through similar steps as in Example 32 byusing tubes 3 having an inner diameter of 30 μm, colored particles ofca. 0.5-1.0 μm and first electrodes 8 and second electrodes 7 in smallerwidths of 20 μm and 10 μm, respectively.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using narrower electrodes,the response time could be reduced to 5 msec or shorter with no displayirregularity due to localization of the colored electrophoreticparticles.

According to this embodiment, the effects of First and Fifth embodimentscan be attained in combination.

Seventh Embodiment

FIG. 55 is a schematic perspective view of an electrophoretic displaydevice according to this embodiment, and FIGS. 56A and 56B are partialsectional views thereof for illustrating an operation principle thereof.

This embodiment illustrated in FIGS. 55-60 is different from Fifthembodiment described with reference to FIGS. 39 to 43 in that each tube3 is provided with a plurality of projections 3 a from the inner wallthereof at prescribed intervals for obstructing the movement of coloredelectrophoretic particles 2 in a longitudinal direction thereof. Theother features are substantially identical to those in Fifth embodiment.

Some specific examples according to this embodiment will be describedhereinbelow.

EXAMPLE 39

A display device was prepared through a process as illustrated in FIGS.58A and 59A-59E.

A cylindrical light-transmissive tube 3 of 10 μm-thick PET film havingan inner diameter of 200 μm was locally periodically heated by causingheat shrinkage to be provided with inner wall projections 3 a at a pitchof 180 μm providing constricted inner wall diameters of 100-150 μm. Onan outer surface of and along a longitudinal generatrix of the tube 3, a200 nm-thick and 100 μm-wide Al first electrode 8 was formed by vacuumevaporation (FIGS. 57A and 57B).

The thus-processed tube 3 was then filled with a display medium DMcomprising a white insulating liquid 1 of silicone oil dyed with anoil-soluble white dye and 3 wt. % of black electrophoretic particles 2of a polystyrene-carbon mixture having particle sizes of 1-2 μm in amanner as illustrated in FIG. 58A, i.e., by dipping one end of the tube3 having inner wall projections 3 a into a bath of the display medium DMunder sufficient stirring in a vessel 21 and sucking from the other endof the tube 3. After the filling, both ends of the tube 3 were sealed upby heating.

Separately, on a light-transmissive second substrate 6 of 200 μm-thickPET film, a 300 nm-thick ITO film was formed and patterned byphotolithography including dry etching to form second electrodes 7 of140 μm-wide stripes at a pitch of 150 μm (FIG. 59A).

Then, a plurality of the above-prepared tubes 3 each provided with afirst electrode 8 and filled with the display medium DM were arranged ona first substrate 4 of 200 μm-thick PET film so that the firstelectrodes 8 thereon contacted the first substrate 4 (FIG. 59B but withno film 90).

Then, the above-prepared second substrate 6 provided with the secondelectrodes 7 (FIG. 59A) was placed on the tubes 3 so that the secondelectrodes 7 contacted the tubes 3 and the second electrodes 7 wereperpendicular to the second electrodes 8 and the second substrate 6 waspositionally aligned with the first substrate 4 (FIG. 59C). Further, acasting polypropylene-type heat-curable adhesive was applied between thesubstrates at peripheries of the stacked structure, which was theninstalled within a PET-made outer frame (not shown) and heated at 100°C. via the outer frame while setting a gap between the substrates 4 and6 at 140 μm. As a result, the upper and lower parts of the tubes 3 weremade flat by contact with the substrates 6 and 4, the tubes 3 weredisposed in intimate contact with each other to produce a structure asshown in FIGS. 59D and 59E (but with no films 90). Further, thestructure was provided with a voltage application means to provide adisplay device.

The thus-prepared display device was subjected to a display operation tobe observed from the second substrate 6 side by voltage application of±50 volts between the first and second electrodes 8 and 7. In thisexample, the black particles 2 were positively charged in the insulatingliquid 1 of silicone oil and moved toward an electrode supplied with anegative voltage. As a result, the black particles 2 were moved to thefirst electrodes 8 to provide a white display state when the firstelectrodes were supplied with −50 volts (FIG. 56A). On the other hand,the black particles 2 were moved to the second electrodes 7 to provide ablack display state when the second electrodes 7 were supplied with −50volts (FIG. 56B). The response time was 30 msec or shorter. No displayirregularity due to localization of the colored particles 2 wasobserved.

EXAMPLE 40

A display device was prepared through a process as illustrated in FIG.58B and FIGS. 60A-60D.

On an outer surface of and along a longitudinal generatrix of acylindrical light-transmissive tube 3 of 10 μm-thick PET film having aninner diameter of 100 μm used in Example 39, a 10 μm-thick and 100μm-wide stripe first electrode 8 of Ag paste was formed by printing.Further, at parts free from the first electrode 8 on the outer surfaceof the tube 3, 30 μm-high external projections 9 b of PET were formed ata pitch of 300 μm along a longitudinal generatrix of the tube 3. Then,the tube 3 was filled with the same display medium DM as used in Example39 in a manner illustrated in FIG. 58B, i.e., by dipping one end of thetube 3 containing black electrophoretic particles 2 attached to theinner wall thereof into a bath 21 of the white-dyed insulating liquid 1and introducing the white insulating liquid 1 by sucking the other endof the tube 3. After filling both ends of the tube 3 were sealed byheating.

After providing a second substrate 6 with second electrodes 7 similarlyas in Example 39 (FIG. 60A), a plurality of the tubes 3 process in theabove-described manner were arranged in contact with each other on afirst substrate 4 identical to the one used in Example 39 so that thefirst electrodes 8 on the tubes 3 contacted the first substrate 4 (FIG.60B but with no films 90), and the above-prepared second substrate 6provided with the second electrodes 7 were placed thereon so that thesecond electrodes 7 contacted the tubes 3 (FIG. 60C but with no films90).

The structure was then installed in an outer frame, and the substrates 4and 6 were bonded to each other while setting a gap of 200 μmtherebetween under heating similarly as in Example 39. As a result, thetubes 3 were disposed in intimate contact with each and with their upperand lower surfaces made flat and in intimate contact with the secondsubstrate 6 and first substrate 4 while the side walls were providedwith inner projections 3 a by pressing with the outer projections 9 bprovided on the tubes 3.

The thus-prepared display device was subjected to a display operation inthe same manner as in Example 39, whereby a good display free fromdisplay irregularity due to localization of the colored particles wasrealized at a response time of 30 msec or shorter.

EXAMPLE 41

A display device was produced in the following manner through a processsimilar to the one illustrated in FIGS. 43A-43C.

A light-transmissive tube 3 of 8 μm-thick PET film having a squaresection of 200 μm×200 μm with round corners was locally periodicallyheated for causing heat shrinkage to be provided with 30 μm-highcircumferential inner wall projections 3 a at a pitch of 250 μm in thelongitudinal direction of the tube 3. On an outer side in thelongitudinal direction of the tube 3, a 300 nm-thick and 100 μm-widestripe of ITO first electrode 8 was formed by ion plating. Further, onthe opposite side of the tube 3 with respect to the ITO electrode side,200 nm-thick Al conductive films 90 of 150×150 μm-square were formed ata pitch of 200 μm along a longitudinal direction of the tube 3.

The tube 3 was filled with the same display medium DM as used in Example39, and a plurality of the tubes 3 thus prepared were arranged incontact with each other on the same first substrate 8 as in Example 39(FIG. 43B). Further thereon, the same second electrode 6 provided withsecond substrates 7 as in Example 24 (FIG. 43A) was placed so that thesecond substrates 7 contacted the ITO films 9 formed on the tubes 3.Further, the stacked structure after alignment of the substrates 4 and 6and application of an adhesive was installed within an outer frame andheated for bonding of the substrates while setting a gap between thesubstrates of 220 μm to provide a structure as shown in FIG. 43C (butfurther including the inner projections 3 a). The structure was furtherprovided with a voltage application means to complete a display device.

The thus-prepared display device was subjected to a display operation inthe same manner as in Example 39, whereby a good display free fromdisplay irregularity due to localization of the colored particles 2 wasperformed at a response time of 30 msec or shorter.

EXAMPLE 42

A light-transmissive cylindrical tube 3 of 10 μm-thick PET film havingan inner diameter of 200 μm was locally periodically heated to providecircumferential inner wall projections 3 a giving an inner diameter of100-150 μm. Then, on an outer wall of the tube 3, a 100 μm-wide stripefirst electrode 8 of 200 nm-thick Pt was formed.

A plurality of tubes thus-treated were then filled with three colors ofdisplay media DM comprising three colors of insulating liquid 1 ofsilicone oil dyed with oil-soluble dyes of yellow, magenta and cyan,respectively, and 2 wt. % of white electrophoretic particles 2 of 1 to 2μm-dia. TiO₂ particles in a manner as illustrated in FIG. 58B. After thefilling, both ends of each tube were sealed by heating. Thus, threetypes of tubes 3 containing three colors of insulating liquid 1 wereprepared.

Then, the thus-prepared three colors of tubes 3 were arranged in aprescribed order on a first substrate 4 provided with first electrodes8, and a second substrate 6 provided with second electrodes 7 was placedthereon and bonded to the first substrate 4 in the same manner as inExample 39, followed by provision of a voltage application means tocomplete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to display the respective colorsof the insulating liquids when the first electrodes were supplied with+50 volt and moved to the second electrodes 7 to provide a white displaystate when the second electrodes 7 were supplied with +50 volts.Accordingly, by changing a combination of voltages applied to the firstelectrode 8 and the second electrode 7 at respective pixels, a colordisplay could be performed as combinations of yellow, magenta and cyan.The response time was 30 msec or shorter, and no display irregularitydue to localization of the colored particles 2 was observed.

EXAMPLE 43

A plurality light-transmissive PET tubes 3 used in Example 39 werefilled with three display media comprising a white insulating liquid 1of dyed silicone oil and three colors of 1 to 2 μm-dia. electrophoreticparticles 2 formed as mixture of polystyrene and one of yellow, magentaand cyan colorants in a manner as illustrated in FIG. 58B.

Then, each tube 3 filled with a display medium was provided with innerwall projections giving a remaining inner diameter of 50-100 μm at apitch of 200 μm along the length of the tube 3 by press-forming using apressing tool while heating the tube 3. Further, on the outer surface ofthe tube 3, a 100 μm-wide stripe first electrode 8 of 200 nm-thick Agwas formed. Thus, three colors of tubes 3 each provided with a firstelectrode 8 were prepared.

Then, the thus-prepared three colors of tubes 3 were arranged in aprescribed order on a 200 μm-thick first substrate 4, identical to theone used in Example 39, and a second substrate 6 provided with secondelectrodes 7 was placed thereon and bonded to the first substrate 4 inthe same manner as in Example 39, followed by provision of a voltageapplication means to complete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As thecolored particles 2 were positively charged in the silicone oil 1, theparticles 2 were moved to the first electrodes 8 to display a whitecolor of the insulating liquid 1 when the first electrodes were suppliedwith −50 volt and moved to the second electrodes 7 to display therespective colors of the colored particles 2 when the second electrodes7 were supplied with +50 volts. Accordingly, by changing a combinationof voltages applied to the first electrode 8 and the second electrode 7at respective pixels, a color display could be performed as combinationsof yellow, magenta and cyan. The response time was 30 msec or shorter,and no display irregularity due to localization of the colored particles2 was observed.

EXAMPLE 44

A display device was prepared through similar steps as in Example 39 byusing tubes 3 having an inner diameter of 30 μm, colored particles ofca. 0.5-1.0 μm and a smaller gap of 25 μm between the substrates.

The thus-prepared display device was driven by application of ±50 volts.As a result of shorter migration distance by using a smaller gap betweenthe substrates, the response time could be reduced to 5 msec or shorterwith no display irregularity due to localization of the coloredelectrophoretic particles.

According to this embodiment, the effects of Third and Fifth embodimentscan be attained in combination.

Eighth Embodiment

FIG. 61 is a schematic perspective view of an electrophoretic displaydevice according to this embodiment, and FIGS. 62A and 62B (transversesectional views) and FIGS. 63A and 63B (longitudinal sectional views)are partial sectional views thereof for illustrating an operationprinciple thereof.

This embodiment illustrated in FIGS. 61 to 70 is different from Sixthembodiment described with reference to FIGS. 44 to 54 in that each tube3 is provided with a plurality of projections 3 a from the inner wallthereof at prescribed intervals for obstructing the movement of coloredelectrophoretic particles 2 in a longitudinal direction thereof. Theother features are substantially identical to those in Sixth embodiment.

Some specific examples according to this embodiment will be describedhereinbelow.

EXAMPLE 45

A display device having a structure as shown in FIGS. 61 to 63 wasprepared through a process as illustrated in FIGS. 67A-67B and 68A-68E.

A cylindrical light-transmissive tube 3 of 10 μm-thick PET having aninner diameter of 200 μm was locally periodically heated for causingheat-shrinkage to be provided with inner wall projections 3 a at a pitchof 180 μm providing constricted inner wall diameter of 100-150 μm. On anouter surface of and along a longitudinal generatrix of the deformedtube 3, a 0.2 μm-thick and 50 μm-wide Al second electrode 7 was formedby vacuum evaporation (FIGS. 67A and 67B).

The thus-processed tube 3 was then filled with a display medium DMcomprising a transparent insulating liquid 1 of silicone oil and 3 wt. %of black electrophoretic particles 2 of a polystyrene-carbon mixturehaving particle sizes of 1-2 μm in a manner as illustrated in FIG. 58A,i.e., by dipping one end of the tube 3 into a bath of the display mediumDM under sufficient stirring in a vessel 21 and sucking from the otherend of the tube 3. After the filling, both ends of the tube 3 weresealed up by heating.

Separately, on a first substrate 4 of 200 μm-thick PET film, a 300nm-thick ITO film was formed and patterned by photolithography includingdry etching to form first electrode 8 of 150 μm-wide stripes at a pitchof 200 μm, which were then coated with a 3 μm-thick insulation layer 5of acrylic resin colored with TiO₂ fine particles (FIG. 68A).

Then, a plurality of the above-prepared tubes 3 each provided with asecond substrate 7 and filled with the display medium DM were arrangedon the first substrate 4 so that the tubes 3 were perpendicular to thefirst electrodes 8 and the second electrodes thereon contacted theinsulating layer 5 on the first substrate 4 (FIG. 68B).

Then, a second substrate 6 of 200 μm-thick PET film was placed on thetubes 3 so that the second electrodes 7 contacted the tubes 3 andpositionally aligned with the first substrate 4 (FIG. 68C). Further, acasting polypropylene-type heat-curable adhesive was applied between thesubstrates at peripheries of the stacked structure, which was theninstalled within a PET-made outer frame (not shown) and heated at 100°C. via the outer frame while setting a gap between the substrates 4 and6 at 150 μm. As a result, the upper and lower parts of the tubes 3 weremade flat by contact with the substrates 6 and 4, the tubes 3 weredeformed and disposed in intimate contact with each other while reducinga distance between the upper and lower portions of the projections 3 ato produce a structure as shown in FIGS. 68D and 68E. Further, thestructure was provided with a voltage application means to provide adisplay device.

The thus-prepared display device was subjected to a display operation tobe observed from the second substrate 6 side by voltage application of±50 volts between the first and second electrodes 8 and 7. In thisexample, the black particles 2 were positively charged in the insulatingliquid 1 of silicone oil and moved toward an electrode supplied with anegative voltage. As a result, the black particles 2 were moved to thefirst electrodes 8 to provide a black display state when the firstelectrodes were supplied with −50 volts (FIGS. 62A and 63A). On theother hand, the black particles 2 were moved to the second electrodes 7to provide a grayish white display state when the second electrodes 7were supplied with −50 volts (FIGS. 62B and 63B). The response time was30 msec or shorter. No display irregularity due to localization of thecolored particles 2 was observed.

EXAMPLE 46

A display device was prepared through a process as illustrated in FIGS.67C-67D and 69A-69D.

A cylindrical light-transmissive PET tube 3 of 200 μm in inner diameterwas filled with the same display medium DM as in Example 45 in a manneras illustrated in FIG. 58B. The tube 3 was locally periodically heatedin a longitudinal direction for causing local heat-shrinkage, whiletaking care of not causing the denaturation of the display mediumtherein, to form local inner wall projections having a height of 40 μmat a pitch of ca. 200 μm.

Then, on an outer wall of and on the same side as the inner wallprojections of the tube 3, a 0.2 μm-thick and ca. 50 μm-wide secondelectrode 7 of Cu stripe was applied and coated with a 0.3 μm-thickpolyimide layer 5 a by painting (FIGS. 67C and 67D).

Then, in the same manner as in Example 45, a first substrate 4 wasprovided with first electrodes 8 (FIG. 69A), and a plurality of theabove-processed tubes 3 were arranged thereon so that the longitudinaldirection of the tubes 3 was perpendicular to the stripe firstelectrodes 8 and the insulating layers 5 a on the second electrodes 7contacted the first electrodes 8 (FIG. 69B).

Thereafter, a second substrate 6 of PET film as used in Example 45further provided with masking patterns (not shown) at partscorresponding the second electrodes 7 was placed thereon, and afteralignment of the substrates 4 and 6, the substrates were bonded to eachother while setting a gap therebetween at 200 μm within an outer frameto form a structure shown in FIG. 69D, which was then provided with avoltage application means to complete a display device.

The thus-prepared display device was subjected to a display operationfor observation from the second substrate 6 side under application of±50 volts in the same manner as in Example 45. As a result, a gooddisplay similarly as in Example 45 was performed at a response time of30 msec or shorter while causing no display irregularity due tolocalization of the colored particles 2.

EXAMPLE 47

A color display device having an organization as illustrated in FIG. 61was prepared through a process as illustrated in FIGS. 68A-68E.

A light-transmissive tube 3 of PES having an inner diameter of 200 μmwas locally periodically heated in a longitudinal direction for causinglocal heat-shrinkage to provide 40 μm-high local inner wall projectionsat a pitch of ca. 200 μm. Then, on an outer wall of the tube 3, a darkblack titanium carbide film was formed and patterned by photolithographyincluding dry etching to form a 50 μm-wide and 0.3 μm-thick stripesecond electrode 7 (FIGS. 67A and 67B).

A plurality of the thus-prepared tubes 3 were filled with three colorsof display media DM comprising three colors of insulating liquid 1 ofsilicone oil dyed with yellow, magenta and cyan dyes, respectively, and3 wt. % of white particles 2 of TiO₂ having particle sizes of 1-2 μm, ina manner as illustrated in FIG. 58A, followed by sealing of both ends.Thus, three colors of tubes 3 were prepared.

Separately, a first substrate 4 identical to the one used in Example 45was provided with 50 μm-wide first electrodes 8 of ITO stripes andfurther coated with a 5 μm-thick transparent polyimide layer 5 otherwisein the same manner as in Example 45. Thereon, the above-processed threecolors of tubes 3 were arranged in a prescribed order so as to beperpendicular to the first electrodes 8 and so that the secondelectrodes 7 contacted the insulating layer 5 on the first substrate 4(FIG. 68B), and a second substrate 6 identical to the one used inExample 45 was further disposed thereon (FIG. 68C). Thereafter, thestructure was installed within an outer frame and subjected to bondingof the substrates 4 and 6, followed by provision of a voltageapplication means, in the same manner as in Example 45.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the first substrate 4 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a white display statewhen the first electrodes were supplied with +50 volt and moved to thesecond electrodes 7 to display the respective colors of the insulatingliquids 1 when the second electrodes 7 were supplied with +50 volts.Accordingly, by changing a combination of voltages applied to the firstelectrode 8 and the second electrode 7 at respective pixels, a colordisplay could be performed as combinations of yellow, magenta and cyan.The response time was 30 msec or shorter, and no display irregularitydue to localization of the colored particles 2 was observed.

EXAMPLE 48

A color display device having an organization as illustrated in FIG. 64was prepared through a process similar to the one illustrated in FIGS.69A-69D.

A plurality of light-transmissive tubes 3 of PET used in Example 45 werefitted with three colors of display media DM prepared as mixtures of aninsulating liquid 1 of silicone oil and 1 to 2 μm-dia. colored particlescomprising polystyrene in mixture with colorants of yellow, magenta andcyan, respectively, in a manner as illustrated in FIG. 58B.

Each tube 3 filled with a display medium was subjected to heat-shrinkageby using a pressing tool to provide circumferentially extending 30μm-high inner wall projections at a pitch of 200 μm in a longitudinaldirection of the tube 3.

Then, on an outer surface of the tube 3, a 0.3 μm-thick and 50 μm-widestripe of second electrode 7 of dark black titanium carbide was formedand covered with a 0.5 μm thick and 80 μm-wide transparent polyimidelayer 5 a (FIGS. 67C and 67D).

Separately, a first substrate 4 of 200 μm-thick PET film was providedwith first electrodes 8 of 300 nm-thick and 150 μm-wide ITO stripes at apitch of 200 μm and a 5 μm-thick transparent polyimide insulating layer5 (not shown) (close to FIG. 69A).

On the thus-processed first substrate 4, the above-prepared three colorsof the tubes 3 each provided with a second electrode 7 and an insulatinglayer 5 a were arranged in a prescribed order so that the secondelectrodes 7 thereon were perpendicular to the first electrodes 8 andthe insulating layers 5 a thereon contacted the first substrate 4 (FIG.69B).

Separately, on a second substrate 6 of 200 μm-thick PET film, a darkblack-colored 300 nm-thick titanium carbide film was formed andpatterned by photolithography including dry etching to form maskingstripes 16 (not shown) corresponding to second electrodes 7. Thethus-treated second substrate 6 was disposed on the tubes 3 arranged onthe first substrate 4 with the masking stripes 16 downward so as to bealigned with the second electrodes 7 after deformation of the tubes 3(close to FIG. 69C). Then, the structure was installed within an outerframe, bonding of the substrates and provision of a voltage applicationmeans in the same manner as in Example 45 to complete a display device.

The thus-prepared display device was subjected to voltage application of±50 volts for observation from the second substrate 6 side. As thecolored particles 2 were positively charged in the silicone oil 1, theparticles 2 were moved to the first electrodes 8 to display therespective colors of the colored particles 2 when the first electrodeswere supplied with −50 volt and moved to the second electrodes 7 todisplay a white color of the first electrodes 8 when the secondelectrodes 7 were supplied with +50 volts. Accordingly, by changing acombination of voltages applied to the first electrode 8 and the secondelectrode 7 at respective pixels, a color display could be performed ascombinations of yellow, magenta and cyan. The response time was 30 msecor shorter, and no display irregularity due to localization of thecolored particles 2 was observed.

EXAMPLE 49

A color display having an organization of FIG. 65A was prepared througha process as illustrated in FIGS. 70A-70D.

Tubes 3 each provided with a second electrode 7 and filled with adisplay medium were formed in the same manner as in Example 45 exceptfor reducing the tube inner diameters to 100 μm and using a displaymedium comprising an insulating liquid 1 of silicone oil and 3 wt. % of1 to 2 μm-dia. white colored particles 2 of TiO₂.

Separately, a light-transmissive first substrate 4 of 200 μm-thick PETfilm was provided with 0.3 μm-thick and 150 μm-wide stripe firstelectrodes 8 of ITO at a pitch of 200 μm and coated with a 0.2 μm-thicktransparent polyimide layer (as a lower half of 5), on which coloredlayers 17, 18 and 19 of yellow, magenta and cyan respectively in theform of 0.2 μm-thick and 100 μm-wide stripes were formed in a prescribedorder and so as to extend perpendicularly to the first electrodes 8 andthen further coated with a 0.5 μm-thick transparent polyimide layer(upper half of 5), thereby providing a structure of processed firstsubstrate 4 as shown in FIG. 70A.

Then, the above-prepared tubes 3 each provided with a second electrode 7and filled with a display medium were arranged on the above-processedfirst substrate 4 so that each second electrodes 7 thereon was parallelto the color stripes 17 (18, 19) and disposed between adjacent colorstripes 17 (18, 19) (FIG. 70B).

Then, a second substrate 6 identical to the one used in Example 45 wasplaced thereover (FIG. 70C), and the structure was installed within anouter frame, bonding of the substrates 4 and 6, and provision of avoltage application means in the same manner as in Example 32 to providea display device having a structure as shown in FIG. 65A (FIG. 70D).

The thus-prepared display device was subjected to voltage application of±60 volts for observation from the second substrate 6 side. As the whiteparticles 2 were negatively charged in the silicone oil 1, the particles2 were moved to the first electrodes 8 to provide a white display statewhen the first electrodes were supplied with +60 volt and moved to thesecond electrodes 7 to display the respective colors of the color layers17, 18 and 19 when the second electrodes 7 were supplied with +50 volts.Accordingly, by changing a combination of voltages applied to the firstelectrode 8 and the second electrode 7 at respective pixels, a colordisplay could be performed as combinations of yellow, magenta and cyan.The response time was 30 msec or shorter, and no display irregularitydue to localization of the colored particles 2 was observed.

Further, in case where the display device was driven by reducing thevoltage application time to 5 msec, the brightness of the respectivecolors could be reduced to nearly a half, whereby a gradational colordisplay characteristic by various selection voltage application time wasconfirmed.

EXAMPLE 50

A display device was prepared through similar steps as in Example 45 byusing tubes 3 having an inner diameter of 30 μm, colored particles ofca. 0.5-1.0 μm and first electrodes 8 and second electrodes 7 in smallerwidths of 20 μm and 10 μm, respectively.

The thus-prepared display device was driven by application of ±60 volts.As a result of shorter migration distance by using narrower electrodes,the response time could be reduced to 5 msec or shorter with no displayirregularity due to localization of the colored electrophoreticparticles.

According to this embodiment, the effects of Third and Sixth embodimentscan be attained in combination.

1. A display device, comprising: a first substrate and a secondsubstrate disposed opposite to each other; a display medium comprisingan insulating liquid and electrophoretic colored particles dispersedtherein and disposed between the first and second substrates; a firstelectrode and a second electrode for applying a voltage to the displaymedium so as to move the colored particles between the first and secondelectrodes to effect a display depending on a voltage applied to thefirst and second electrodes, with the first and second electrodesarranged to provide a matrix-type display device; and a plurality oflight-transmissive insulating tubes containing different colors of thedisplay medium and arranged in a prescribed order of the colors betweenthe first and second substrates with the tubes extending in onedirection of the matrix-type display device, wherein the secondelectrode is disposed to divide the tubes into plural sections in theirlongitudinal direction so that the respective sections can beindependently driven.
 2. A display device according to claim 1, whereinboth the first electrode and the second electrode are disposed on thefirst substrate, and the colored particles are moved parallel to thesubstrates by the voltage applied between the first and secondelectrodes.
 3. A display device according to claim 1, wherein theinsulating liquid and the colored particles of the display medium areintroduced simultaneously into the tubes.
 4. A display device accordingto claim 1, wherein the insulating liquid and the colored particles ofthe display medium are introduced separately into the tubes.
 5. Adisplay device according to claim 1, wherein the tubes are flexible andhave an original cross-sectional shape of a circle or an oval and aredisposed between the substrates, with a diameter parallel to thesubstrates being equal to or larger than a diameter perpendicular to thesubstrates.
 6. A display device according to claim 1, wherein the tubescomprise a polymer.
 7. A display device according to claim 1, whereinsaid first substrate is provided with a colored layer thereon.
 8. Adisplay device according to claim 7, wherein the colored layer has acolor different from that of the colored particles.
 9. A display deviceaccording to claim 1, wherein the insulating liquid in each tube iscolored in any one of yellow, magenta and cyan.
 10. A display deviceaccording to claim 1, wherein the plurality of tubes contain differentcolors of the insulating light and are arranged in a prescribed order ofthe colors between the first and second substrates.
 11. A display deviceaccording to claim 1, wherein the colored particles in each tube iscolored in any one of yellow, magenta and cyan.
 12. A display deviceaccording to claim 1, wherein the plurality of tubes contain differentcolors of the colored particles and are arranged in a prescribed orderof the colors between the first and second substrates.
 13. A displaydevice according to claim 1, wherein at least one of the first andsecond substrates is light-transmissive.
 14. A display device accordingto claim 1, wherein the first and second substrates each comprise apolymer film.
 15. A display device according to claim 1, wherein thefirst electrode is light-transmissive.
 16. A display device according toclaim 1, wherein at least one of the colored particles, the electrodesand the insulating light is colored in plural colors to effect a colordisplay.
 17. A display device according to claim 1, wherein the firstelectrodes and the second electrodes are disposed on the first substrateand the second substrate, respectively, and the colored particles aremoved in a direction vertical to the substrates by the voltage appliedbetween the first and second electrodes.
 18. A display device,comprising: a first substrate and a second substrate disposed oppositeto each other; a display medium comprising an insulating liquid andelectrophoretic colored particles dispersed therein and disposed betweenthe first and second substrates; a first electrode and a secondelectrode for applying a voltage to the display medium so as to move thecolored particles between the first and second electrodes to effect adisplay depending on a voltage applied to the first and secondelectrodes, with the first and second electrodes arranged to provide amatrix-type display device, and a plurality of light-transmissiveinsulating tubes containing different colors of the display medium, eachtube having a projection part to obstruct the movement of the coloredparticles at its inner wall disposed at an interval in a longitudinaldirection, and the plurality of light-transmissive insulating tubes arearranged in a prescribed order of the colors between the first andsecond substrates, with the tubes extending in one direction of thematrix-type display device, wherein the second electrode is disposed todivide the tubes into plural sections in their longitudinal direction sothat the respective sections can be independently driven.
 19. A displaydevice according to claim 18, wherein the colored particles are movedparallel to the substrates within a section partitioned by neighboringtwo of the inner wall projections by the voltage applied between thefirst and second electrodes.
 20. A display device according to claim 18,wherein the first and second electrodes are both formed on the firstsubstrate, and the inner wall projections are formed at least on a sideof the inner wall of each tube close to the first substrate.
 21. Adisplay device according to claim 18, wherein the tubes are formed of apolymer.
 22. A display device according to claim 18, wherein the innerwall projections have been formed by heat shrinkage of each tube priorto filling with the display medium.
 23. A display device according toclaim 18, wherein the inner wall projections are formed by pressing eachtube before or after filling with the display medium.
 24. A displaydevice according to claim 18, wherein at least the first substrate isprovided with projections, and the inner wall projections are providedto each tube by pressing the tubes by the projections when the tubes aredisposed in intimate contact with each other between the substrates. 25.A display device according to claim 18, wherein the first electrode islight-transmissive, and the first substrate is provided with a coloredlayer and a light reflection layer in lamination.
 26. A display deviceaccording to claim 18, wherein at least one of the first electrode, thecolored layer and the light reflection layer is colored in a colordifferent from that of the colored particles.
 27. A display deviceaccording to claim 18, wherein the plurality of tubes contain differentcolors of the insulating liquid and are arranged in a prescribed orderof the colors between the first and second substrates.
 28. A displaydevice according to claim 18, wherein the plurality of tubes containdifferent colors of the colored particles and are arranged in aprescribed order of the colors between the first and second substrates.29. A display device according to claim 18, wherein the second electrodeis colored.
 30. A display device according to claim 18, wherein at leastone of the first and second substrates is light-transmissive.
 31. Adisplay device according to claim 18, wherein the first and secondsubstrates each comprise a polymer film.
 32. A display device accordingto claim 18, wherein at least one of the colored particles, theelectrodes and the insulating liquid is colored in plural colors toeffect a color display.
 33. A display device according to claim 18,wherein the colored particles are moved vertically to the substrateswithin a section partitioned by neighboring two of the inner wallprojections by the voltage applied between the first and secondelectrodes.